PROSITE documentation PDOC00656
Uroporphyrin-III C-methyltransferase signatures


Uroporphyrin-III C-methyltransferase (EC (SUMT) [1,2] catalyzes the transfer of two methyl groups from S-adenosyl-L-methionine to the C-2 and C-7 atoms of uroporphyrinogen III to yield precorrin-2 via the intermediate formation of precorrin-1. SUMT is the first enzyme specific to the cobalamin pathway and precorrin-2 is a common intermediate in the biosynthesis of corrinoids such as vitamin B12, siroheme and coenzyme F430.

The sequences of SUMT from a variety of eubacterial and archaebacterial species are currently available. In species such as Bacillus megaterium (gene cobA), Pseudomonas denitrificans (cobA) or Methanobacterium ivanovii (gene corA) SUMT is a protein of about 25 to 30 Kd. In Escherichia coli and related bacteria, the cysG protein, which is involved in the biosynthesis of siroheme, is a multifunctional protein composed of a N-terminal domain, probably involved in transforming precorrin-2 into siroheme, and a C-terminal domain which has SUMT activity.

The sequence of SUMT is related to that of a number of P. denitrificans and Salmonella typhimurium enzymes involved in the biosynthesis of cobalamin which also seem to be SAM-dependent methyltransferases [3,4]. The similarity is especially strong with two of these enzymes: cobI/cbiL which encodes S-adenosyl-L-methionine--precorrin-2 methyltransferase and cobM/cbiF whose exact function is not known.

We developed two signature patterns for these enzymes. The first corresponds to a well conserved region in the N-terminal extremity (called region 1 in [1,3]) and the second to a less conserved region located in the central part of these proteins (this pattern spans what are called regions 2 and 3 in [1,3]).


Yeast diphthine synthase (EC (gene DPH5) seems to be [5] evolutionary related to SUMT, but is not detected by the above patterns.

Last update:

December 2004 / Pattern and text revised.


Technical section

PROSITE methods (with tools and information) covered by this documentation:

SUMT_1, PS00839; Uroporphyrin-III C-methyltransferase signature 1  (PATTERN)

SUMT_2, PS00840; Uroporphyrin-III C-methyltransferase signature 2  (PATTERN)


1AuthorsBlanche F. Robin C. Couder M. Faucher D. Cauchois L. Cameron B. Crouzet J.
TitlePurification, characterization, and molecular cloning of S-adenosyl-L-methionine: uroporphyrinogen III methyltransferase from Methanobacterium ivanovii.
SourceJ. Bacteriol. 173:4637-4645(1991).
PubMed ID1856165

2AuthorsRobin C. Blanche F. Cauchois L. Cameron B. Couder M. Crouzet J.
TitlePrimary structure, expression in Escherichia coli, and properties of S-adenosyl-L-methionine:uroporphyrinogen III methyltransferase from Bacillus megaterium.
SourceJ. Bacteriol. 173:4893-4896(1991).
PubMed ID1906874

3AuthorsCrouzet J. Cameron B. Cauchois L. Rigault S. Rouyez M.-C. Blanche F. Thibaut D. Debussche L.
TitleGenetic and sequence analysis of an 8.7-kilobase Pseudomonas denitrificans fragment carrying eight genes involved in transformation of precorrin-2 to cobyrinic acid.
SourceJ. Bacteriol. 172:5980-5990(1990).
PubMed ID2211521

4AuthorsRoth J.R. Lawrence J.G. Rubenfield M. Kieffer-Higgins S. Church G.M.
TitleCharacterization of the cobalamin (vitamin B12) biosynthetic genes of Salmonella typhimurium.
SourceJ. Bacteriol. 175:3303-3316(1993).
PubMed ID8501034

5AuthorsMattheakis L.C. Shen W.H. Collier R.J.
TitleDPH5, a methyltransferase gene required for diphthamide biosynthesis in Saccharomyces cerevisiae.
SourceMol. Cell. Biol. 12:4026-4037(1992).
PubMed ID1508200

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