Literature summary for 2.1.1.296 extracted from

Arhin, G.; Ullu, E.; Tschudi, C.
2'-O-Methylation of position 2 of the trypanosome spliced leader cap 4 is mediated by a 48 kDa protein related to vaccinia virus VP39 (2006), Mol. Biochem. Parasitol., 147, 137-139.

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Cloned(Commentary)

Cloned (Comment)	Organism
primer extension analysis, functional expression observed of the MT48 gene tagged at the C-terminus with an HA epitope in mt48-/- cells	Trypanosoma brucei

Protein Variants

Protein Variants	Comment	Organism
additional information	silencing of TbMT48 mRNA by RNAi downregulation does not produce a lethal phenotype, as MT48-RNAi trypanosomes remain viable even after 10 days of tetracycline induction, generation of MT48 KO clonal cell lines by homologous recombination with PCR-generated cassettes. An observed defect in cap 4 modification, specific for MT48 ablation, can be complemented by reintroduction of a copy of the MT48 gene into mt48-/- cells	Trypanosoma brucei

Molecular Weight [Da]

Molecular Weight [Da]	Molecular Weight Maximum [Da]	Comment	Organism
48000	-	x * 48000, SDS-PAGE	Trypanosoma brucei

Natural Substrates/ Products (Substrates)

Natural Substrates	Organism	Comment (Nat. Sub.)	Natural Products	Comment (Nat. Pro.)	Rev.	Reac.
additional information	Trypanosoma brucei	a conventional 5'-terminal structure of eukaryotic mRNAs consists of a 7-methylguanosine (m7G) moiety linked to the first transcribed nucleotide by a 5' to 5' triphosphate bridge resulting in the structure m7GpppN, which is referred to as cap 0, and most often the first and second transcribed nucleotide carry 2'-O-methyl groups (cap 1 and cap 2 structures, respectively). The cap2 methyltransferase, EC 2.1.1.296 transfers the methyl group to the second nucleotide. In contrast, four nucleotides adjacent to the m7G cap are methylated at the SL RNA 5' end to generate a cap 4 structure: m7G-ppp-N6,N6,2'-O-trimethyladenosine-p-2'-O-methyladenosine-p-2'-O-methylcytosine-p-N3,2'-O-methyluridine. The cap 4 structure seems to be restricted to the family Trypanosomatidae	?	-	?

Organism

Organism	UniProt	Comment	Textmining
Trypanosoma brucei	Q385S9	-	-

Substrates and Products (Substrate)

Substrates	Comment Substrates	Organism	Products	Comment (Products)	Rev.	Reac.
additional information	a conventional 5'-terminal structure of eukaryotic mRNAs consists of a 7-methylguanosine (m7G) moiety linked to the first transcribed nucleotide by a 5' to 5' triphosphate bridge resulting in the structure m7GpppN, which is referred to as cap 0, and most often the first and second transcribed nucleotide carry 2'-O-methyl groups (cap 1 and cap 2 structures, respectively). The cap2 methyltransferase, EC 2.1.1.296 transfers the methyl group to the second nucleotide. In contrast, four nucleotides adjacent to the m7G cap are methylated at the SL RNA 5' end to generate a cap 4 structure: m7G-ppp-N6,N6,2'-O-trimethyladenosine-p-2'-O-methyladenosine-p-2'-O-methylcytosine-p-N3,2'-O-methyluridine. The cap 4 structure seems to be restricted to the family Trypanosomatidae	Trypanosoma brucei	?	-	?
additional information	the enzyme builds the cap 4 structure, usage of an assay with digestion with ribonuclease T2, to monitor the presence of 2'-O-modifications at positions +1 to +4 of the SL sequence	Trypanosoma brucei	?	-	?
S-adenosyl-L-methionine + a 5'-(N7-methyl 5'-triphosphoguanosine)-(2'-O-methyl-purine-ribonucleotide)-(ribonucleotide)-[mRNA]	-	Trypanosoma brucei	S-adenosyl-L-homocysteine + a 5'-(N7-methyl 5'-triphosphoguanosine)-(2'-O-methyl-purine-ribonucleotide)-(2'-O-methyl-ribonucleotide)-[mRNA]	-	?

Subunits

Subunits	Comment	Organism
?	x * 48000, SDS-PAGE	Trypanosoma brucei

Synonyms

Synonyms	Comment	Organism
MT48	-	Trypanosoma brucei
TbMT48	-	Trypanosoma brucei

Cofactor

Cofactor	Comment	Organism	Structure
S-adenosyl-L-methionine	binding domain structure, overview	Trypanosoma brucei

General Information

General Information	Comment	Organism
evolution	the enzyme shows significant sequence and structural similarities to vaccinia virus VP39, another cap-specific RNA 2'-O-methyltransferase. TbMT48 or TbMT57 are two protein components of the cap 4 biosynthetic machinery	Trypanosoma brucei
malfunction	an observed defect in cap 4 modification is a specific effect of MT48 ablation	Trypanosoma brucei
additional information	enzyme MT48 structural modeling using the VP39 crystal structure as a template, TbMT48 domains involved in S-adenosyl-methionine and cap binding, overview	Trypanosoma brucei
physiological function	TbMT48 or TbMT57 are two protein components of the cap 4 biosynthetic machinery. The enzymes involved in cap 4 biogenesis, TbMT48 and TbMT57, are encoded by non-essential genes, considering that the SL cap 4 structure is a crucial determinant for trans-splicing competence of the SL RNA	Trypanosoma brucei

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Release 2023.1 (January 2023)