Information on EC 2.1.1.33 - tRNA (guanine46-N7)-methyltransferase

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The expected taxonomic range for this enzyme is: Bacteria, Eukaryota

EC NUMBER
COMMENTARY
2.1.1.33
-
RECOMMENDED NAME
GeneOntology No.
tRNA (guanine46-N7)-methyltransferase
REACTION
REACTION DIAGRAM
COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
S-adenosyl-L-methionine + guanine46 in tRNA = S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
mechanism
-
S-adenosyl-L-methionine + guanine46 in tRNA = S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
-
-
-
REACTION TYPE
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
methyl group transfer
-
-
-
-
SYSTEMATIC NAME
IUBMB Comments
S-adenosyl-L-methionine:tRNA (guanine-N7-)-methyltransferase
The enzyme specifically methylates guanine46 at N7 in tRNA.
SYNONYMS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
7-methylguanine transfer ribonucleate methylase
-
-
-
-
m7G-methyltransferase
-
-
-
-
m7G46 methyltransferase Trm8p/Trm82p
Q03774 and Q12009
-
methyltransferase, transfer ribonucleate guanine 7-
-
-
-
-
N7-methylguanine methylase
-
-
-
-
transfer ribonucleate guanine 7-methyltransferase
-
-
-
-
transfer RNA (m7G46) methyltransferase
O66479
-
transfer RNA (m7G46) methyltransferase
P0A8I5
-
Trm8Trm82 complex
Q03774 and Q12009
-
TrmB
O66479
-
TrmB
O34522
-
TrmB
P0A8I5
TrmB belongs to the Rossmann-fold methyltransferase family
TrMet (m7G46)
-
-
tRNA (m7G46) methyltransferase
O66479
-
tRNA (m7G46) methyltransferase
O34522
-
tRNA (m7G46) methyltransferase
P0A8I5
-
tRNA (m7G46) methyltransferase
Q03774 and Q12009
-
tRNA (m7G46) methyltransferase
-
-
tRNA guanine 7-methyltransferase
-
-
-
-
CAS REGISTRY NUMBER
COMMENTARY
37257-00-4
-
ORGANISM
COMMENTARY
LITERATURE
SEQUENCE CODE
SEQUENCE DB
SOURCE
strain K12
SwissProt
Manually annotated by BRENDA team
strain MRE 600, 2 isoenzymes
-
-
Manually annotated by BRENDA team
Escherichia coli MRE 600
strain MRE 600, 2 isoenzymes
-
-
Manually annotated by BRENDA team
Q03774: subunit Trm82, Q2009: subunit Trm8
Q03774 and Q12009
SwissProt
Manually annotated by BRENDA team
strains BY4743, 33523, 33899 and YM317
-
-
Manually annotated by BRENDA team
Saccharomyces cerevisiae D84
strain D84
-
-
Manually annotated by BRENDA team
strain HB8
-
-
Manually annotated by BRENDA team
GENERAL INFORMATION
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
malfunction
-
absence of m7G46 results in temperature-sensitive growth
malfunction
-
protein synthesis in DELTAtrmB cells is depressed above 70C. At 80C, the DtrmB strain exhibits a severe growth defect
physiological function
-
m7G46 methyltransferase Trm8p/Trm82p acts as a hub of synthetic interactions with several tRNA modification enzymes, resulting in temperature-sensitive growth
physiological function
O66479
long C-terminal region of the thermophilic TrmB protein is involved in the protein stability but does not function in the RNA recognition
physiological function
-
Trm8p is required for m7G modification. Trm82p is required to maintain cellular levels of Trm8p and to stabilize Trm8p in an active conformation
physiological function
-
N7 cap methylation is essential for viral replication
physiological function
-
the m7G46 modification catalyzed by TrmB may act as one of the key factors in tRNA modification network; the m7G46 modification is required for cell viability at high temperatures via a tRNA modification network. The m7G46 modification induces nearly full modification of several modified nucleotides such as Gm18 and m1G37
physiological function
-
N7-MTase plays an important role in SARS-coronavirus replication/transcription
SUBSTRATE
PRODUCT                      
REACTION DIAGRAM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
(Substrate)
LITERATURE
(Substrate)
COMMENTARY
(Product)
LITERATURE
(Product)
Reversibility
r=reversible
ir=irreversible
?=not specified
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
Q03774 and Q12009
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
O66479
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
P0A8I5
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptor: methyl-deficient tRNA from E. coli
-
-
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptor: methyl-deficient tRNA from E. coli
-
ir
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptor: methyl-deficient tRNA from E. coli
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
highly specific for tRNA and S-adenosyl-L-methionine, cannot be replaced by methionine plus ATP, formaldehyde plus tetrahydrofolic acid, methylcobalamin and methyltetrahydrofolic acid
-
ir
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptors: tRNACys, tRNATrp, tRNAPro, tRNAMet, tRNAMet-i and 2 of each tRNAPhe, tRNAVal and tRNALys, methylation at G46 in the extra loop
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptors: methyl-deficient bulk tRNA from E. coli K12met-rel-, tRNAfMet from Bacillus subtilis, formation of 0.8 mol N7-methylguanine residues per mol Bacillus subtilis tRNA, enzyme recognizes and methylates specifically the extra arm unpaired methyl-deficient guanylate residue
-
-
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptor: yeast pre-tRNAPhe
-
-
-
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptor: yeast pre-tRNAPhe
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
extend of methylation is directly proportional to the amount of tRNA added, 0.19% of nucleotide residues are methylated
-
ir
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptor: yeast tRNA1Ala, methylates G located in the extra loop at position 46 from the 5 end of tRNA1Ala
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptor: yeast tRNA1Ala, methylates G located in the extra loop at position 46 from the 5 end of tRNA1Ala
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptor: undermethylated tRNA
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
methyl group acceptor: undermethylated tRNA from Salmonella typhimurium CS 14, NH2- and COOH-group of S-adenosyl-L-methionine as well as the length of hydrocarbon chain connecting them to the aromatic ring of adenosine, chirality at the alpha-C atom and NH2-group of adenosine are important for substrate binding to enzyme
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
tRNA modifying enzyme
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
specific enzyme involved in the maturation of tRNA
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
complex of 2 proteins Trm8 and Trm82 is required for efficient m7G-methyltransferase activity in vitro and in vivo, tRNA site G46 is methylated in vivo
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
Escherichia coli MRE 600
-
methyl group acceptors: methyl-deficient bulk tRNA from E. coli K12met-rel-, tRNAfMet from Bacillus subtilis, formation of 0.8 mol N7-methylguanine residues per mol Bacillus subtilis tRNA, enzyme recognizes and methylates specifically the extra arm unpaired methyl-deficient guanylate residue
-
-
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
Saccharomyces cerevisiae D84
-
methyl group acceptor: methyl-deficient tRNA from E. coli
-
?
additional information
additional information
-
-
not as methyl group acceptors: methyl-deficient DNA from E. coli, polyadenylic acid, polycytidylic acid, polyuridylic acid, polyinosinic acid, copolymers of adenylic acid and uridylic acid and of guanylic acid and cytidylic acid, tobacco mosaic viral RNA, turnip yellow mosaic viral RNA, RNA from bacteriophage f2, CMP, AMP, UMP, GMP, rRNA
-
-
-
additional information
additional information
-
-
complex of 2 proteins Trm8 and Trm82 is required for efficient m7G-methyltransferase activity in vitro and in vivo, but Trm82 is not an absolute requirement for activity in vitro, Trm8 may be the catalytically active subunit
-
-
-
additional information
additional information
-
-
methyl group transfer at the polynucleotide level of tRNA, two m7G tRNA-methyltransferases with different specificities for the extra arm unpaired G in different tRNA species
-
-
-
additional information
additional information
-
-
proteins METTL1 and WDR4 are required for m7G-methyltransferase activity
-
-
-
additional information
additional information
-
Escherichia coli MRE 600
-
methyl group transfer at the polynucleotide level of tRNA, two m7G tRNA-methyltransferases with different specificities for the extra arm unpaired G in different tRNA species
-
-
-
NATURAL SUBSTRATES
NATURAL PRODUCTS
REACTION DIAGRAM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
(Substrate)
LITERATURE
(Substrate)
COMMENTARY
(Product)
LITERATURE
(Product)
REVERSIBILITY
r=reversible
ir=irreversible
?=not specified
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
Q03774 and Q12009
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
O66479
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
P0A8I5
-
-
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
tRNA modifying enzyme
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
specific enzyme involved in the maturation of tRNA
-
?
S-adenosyl-L-methionine + guanine46 in tRNA
S-adenosyl-L-homocysteine + N7-methylguanine46 in tRNA
show the reaction diagram
-
complex of 2 proteins Trm8 and Trm82 is required for efficient m7G-methyltransferase activity in vitro and in vivo, tRNA site G46 is methylated in vivo
-
?
COFACTOR
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
S-adenosyl-L-methionine
-
-
S-adenosyl-L-methionine
-
-
S-adenosyl-L-methionine
-
-
S-adenosyl-L-methionine
-
serves usually as coenzyme
S-adenosyl-L-methionine
-
-
METALS and IONS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
Ca2+
-
activates
Cations
-
mono- and divalent cations activate
K+
-, O34522
contains three potassium ions per asymmetric unit, one in the interface between monomers and one in a region involved in AdoMet binding in the homologous catechol O-MTase, bound to the main chain carbonyls of residues Asn115 and Gly46
Mg2+
-
in presence of Mg2+ 2fold increase of activity
Mn2+
-
activates
INHIBITORS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
methylthioadenosine
-
competitive inhibitor
p-hydroxymercuribenzoate
-
-
S-Adenosyl-D-homocysteine
-
competitive inhibitor, L-enantiomer more potent than D-enantiomer by 2 orders of magnitude
S-adenosyl-DL-homocysteine
-
competitive inhibitor
S-adenosyl-L-cysteine
-
competitive inhibitor
S-adenosyl-L-homocysteine
-
product inhibition, reversed by S-adenosylmethionine
S-adenosyl-L-homocysteine
-
potent competitive product inhibition, L-enantiomer more potent than D-enantiomer by 2 orders of magnitude
S-Inosylhomocysteine
-
weak competitive inhibitor, above 0.5 mM
Spleen phosphodiesterase
-
-
-
Methylthioinosine
-
weak competitive inhibitor, above 0.5 mM
additional information
-
not inhibited by adenosine, L-homocysteine, snake venom phosphodiesterase
-
additional information
-
not inhibited by butylthioadenosine, thioethanoladenosine, isobutylthioadenosine
-
ACTIVATING COMPOUND
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
2-mercaptoethanol
-
activates
S-Inosylhomocysteine
-
activates at 0.05-0.2 mM
Methylthioinosine
-
activates at 0.05-0.2 mM
additional information
-
not activated by spermine
-
KM VALUE [mM]
KM VALUE [mM] Maximum
SUBSTRATE
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
0.00025
-
guanine46 in tRNA
-
pH 7.5, 30C, tRNA variant with substitution of C48 by A
-
0.00035
-
guanine46 in tRNA
-
pH 7.5, 30C, tRNA variant with disruption of tertiary base pairs between D- and T-arms
-
0.0005
-
guanine46 in tRNA
-
pH 7.5, 30C, tRNA variant with disruption of C13-G22-G46 tertiary base pair
-
0.0014
-
guanine46 in tRNA
-
pH 7.5, 30C, tRNA variant with deletion of the anticodon-arm
-
0.0015
-
guanine46 in tRNA
-
pH 7.5, 30C, RNA
-
0.0037
-
guanine46 in tRNA
-
pH 7.5, 30C, tRNA variant with deletion of the aminoacyl-stem
-
0.21
-
methyl deficient tRNA from E. coli
-
-
-
0.016
-
S-adenosyl-L-methionine
-
-
Ki VALUE [mM]
Ki VALUE [mM] Maximum
INHIBITOR
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
IMAGE
SPECIFIC ACTIVITY [µmol/min/mg]
SPECIFIC ACTIVITY MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
3.95
-
-
tRNAfMet from Bacillus subtilis
pH OPTIMUM
pH MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
7.5
8
-
dimethylglutarate buffer
7.5
-
-
assay at
TEMPERATURE OPTIMUM
TEMPERATURE OPTIMUM MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
37
-
-
assay at
37
-
-
30fold higher activity when assayed at 37C than at 30C; assay at
38
-
-
assay at
LOCALIZATION
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
GeneOntology No.
LITERATURE
SOURCE
Escherichia coli MRE 600
-
-
-
-
Manually annotated by BRENDA team
additional information
-
organelle-specific enzyme, not in cytoplasm
-
Manually annotated by BRENDA team
PDB
SCOP
CATH
ORGANISM
Bacillus subtilis (strain 168)
Escherichia coli (strain K12)
Escherichia coli (strain K12)
Escherichia coli (strain K12)
Saccharomyces cerevisiae (strain ATCC 204508 / S288c)
Saccharomyces cerevisiae (strain ATCC 204508 / S288c)
Streptococcus pneumoniae serotype 4 (strain ATCC BAA-334 / TIGR4)
MOLECULAR WEIGHT
MOLECULAR WEIGHT MAXIMUM
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
25000
-
-
glycerol gradient centrifugation
100000
-
-
gel filtration, two m7G tRNA-methyltransferases with different specificities for the extra arm unpaired G in different tRNA species
300000
-
-
gel filtration, two m7G tRNA-methyltransferases with different specificities for the extra arm unpaired G in different tRNA species
SUBUNITS
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
?
P0A8I5
x * 27307, calculated from sequence
dimer
-, O34522
crystallographic studies, gel filtration, dimeric both in crystal and in solution
dimer
-
1 * 33000 (subunit Trm8) + 1 * 50000 (subunit Trm82), association of the Trm8 and Trm82 subunits is translationally controlled in living cells, SDS-PAGE
heterodimer
-
the enzyme contains two protein subunits: TRm8 and TRm82
Crystallization/COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
by hanging drop method, at a resolution of 2.1 A, Rossmann-fold methyltransferase structure with the N-terminal helix folded on the opposite site of the catalytic domain
-, O34522
a truncated protein lacking the first 32 residues of the N-terminus but with an additional His6 tag at the C-terminus is crystallized by hanging-drop vapour-diffusion method using 15% (w/v) PEG 3350 and 150 mM MgSO4, at 10C
P0A8I5
GENERAL STABILITY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
freezing without antifreeze agents inactivates, 30% ethylene glycol at -20C stabilizes
-
ORGANIC SOLVENT
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
Ethylene glycol
-
30% stabilizes at -20C
Ethylene glycol
Saccharomyces cerevisiae D84
-
30% stabilizes at -20C
-
STORAGE STABILITY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
-70C, frozen in liquid nitrogen, at least several months, stable
-
0C, partially purified, 48 h, 15% loss of activity
-
0C, purified, 6 months, about 70% loss of activity
-
Purification/COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
1000fold purification by affinity chromatography on Escherichia coli tRNA Sepharose
-
copurification of 2 proteins, Trm8 and Trm82
-
Ni-NTA column chromatography, Sephadex G-25 gel filtration, ammonium sulfate precipitation, and DE52 column chromatography
-
partial purification by phosphocellulose column
-
partially purified by heat treatment and DE52 column chromatography
-
Cloned/COMMENTARY
ORGANISM
UNIPROT ACCESSION NO.
LITERATURE
expression in Escherichia coli
-, O34522
coexpression of both METTL1 and WDR4 in Saccharomyces cerevisiae
-
expressed in a wheat germ cell-free translation system, active Trm8-Trm82 heterodimer is only synthesized under conditions, in which both Trm8 and Trm82 mRNAs are cotranslated
-
ORF YDL201w encodes Trm8 and ORF YDR165w encodes Trm82, both proteins form a complex with m7G-methyltransferase activity, Trm8 contains a binding domain for S-adenosyl-L-methionine: GXGXG, coexpression of Trm8/Trm82 in Escherichia coli BL21 Codon Plus (DE3) as His6-fusion proteins under control of the Ptac-promoter
-
expressed in Escherichia coli strain BL21 (DE3) Rosetta 2
-
ENGINEERING
ORGANISM
UNIPROT ACCESSION NO.
COMMENTARY
LITERATURE
Glu202Stop
O66479
is unstable to heat treatment as compared to the full-length wild-type enzyme, but has an enzymatic activity
additional information
-, O34522
mutant strain, trmB gene inactivated by an insertion, shows normal growth
additional information
-
strains lacking either Trm8 or Trm82 yield extracts with no detectable enzyme activity, and have severely reduced m7G-modified tRNA in vivo
additional information
-
strains lacking Trm8p/Trm82p tRNA m7G methyltransferase, are temperature-sensitive in synthetic media containing glycerol, trm82-delta strain shows reduced levels of Trm8p, but not of its mRNA, the growth phenotype of trm8 mutants correlates with lack of tRNA m7G methyltransferase activity in vitro and in vivo, bacterial Trm8p orthologs complement the trm8-delta trm82-delta growth phenotype and restore m7G-methyltransferase activity in vitro and in vivo