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mRNA-capping enzyme; HCAP1; HCE; includes: polynucleotide 5'-triphosphatase; mRNA 5'-triphosphatase; TPase; mRNA guanylyltransferase; GTP-RNA guanylyltransferase; GTase (RNGTT, CAP1A)
Function:
- bifunctional mRNA-capping enzyme
- RNA 5'-triphosphatase activity in the N-terminal part
- mRNA guanylyltransferase activity in the C-terminal part
- catalyzes the first two steps of mRNA cap formation
a) removing the gamma-phosphate from the 5'-triphosphate end of nascent mRNA to yield a diphosphate end
b) transferring the GMP moiety of GTP to the 5'-diphosphate terminus
- interacts with SUPT5H & RNMT
- interacts with HIV-1 Tat
5'-phosphopolynucleotide + H2O = polynucleotide + phosphate
GTP + (5')pp-pur-mRNA = diphosphate + G(5')ppp-pur-mRNA
Structure:
- in the N-terminal section, belongs to the non-receptor class of the protein-tyrosine phosphatase family
- in the C-terminal section; belongs to the eukaryotic GTase family
- isoforms 2,3 & 4 lack mRNA 5'-guanylyltransferase activity due to disruptions of the GTase domain
Compartment: nucleus (putative)
Alternative splicing: named isoforms=4
Expression:
- isoform 1 & isoform 4 (at a lesser extent) are expressed in cerebrum, cerebellum, thyroid, lung, heart, liver, kidney, spleen, large intestine, testis, skin & muscle
General
nuclear protein
phosphoprotein
transferase
triphosphatase
Properties
SIZE: entity length = 597 aa
MW = 69 kD
COMPARTMENT: cell nucleus
MOTIF: TPase {1-212}
MOTIF: cysteine residue {C126}
acidic region {195-205}
MOTIF: acidic residue (SEVERAL)
Ser phosphorylation site {S210}
GTase {229-597}
MOTIF: lysine residue {K294}
Database Correlations
OMIM 603512
UniProt O60942
PFAM correlations
Entrez Gene 8732
Kegg hsa:8732
ENZYME correlations
References
UniProt :accession O60942