To improve security and privacy, we are moving our web pages and services from HTTP to HTTPS. To give users of web services time to transition to HTTPS, we will support separate HTTP and HTTPS services until the end of 2017. From January 2018 most HTTP traffic will be automatically redirected to HTTPS. [more...] View this page in https
The homocysteine (Hcy) binding domain is an ~300-residue module which is found
in a set of enzymes involved in alkyl transfer to thiols:
Prokaryotic and eukaryotic B12-dependent methionine synthase (MetH)
(EC 18.104.22.168), a large, modular protein that catalyses the transfer of a
methyl group from methyltetrahydrofolate (CH3-H4folate) to Hcy to form
methionine, using cobalamin as an intermediate methyl carrier.
Mammalian βine-homocysteine S-methyltransferase (BHMT) (EC 22.214.171.124). It
catalyzes the transfer of a methyl group from glycine βine to Hcy,
forming methionine and dimethylglycine.
Plant and fungal AdoMet homocysteine S-methyltransferases (EC 126.96.36.199).
The Hcy-binding domain utilizes a Zn(Cys)3 cluster to bind and activate Hcy.
It has been shown to form a (β/α)8 barrel (see <PDB:1Q7Z>). The Hcy
binding domain barrel is distorted to form the metal- and substrate-binding
sites. To accommodate the substrate, strands 1 and 2 of the barrel are loosely
joined by nonclassic hydrogen bonds; to accommodate the metal, strands 6 and 8
are drawn together and strand 7 is extruded from the end of the barrel. The
cysteines ligating the catalytic zinc atom are located at the C-terminal ends
of strands 6 and 8 [1,2].
The profile we developed covers the entire Hcy domain.
October 2005 / Text revised.
PROSITE method (with tools and information) covered by this documentation:
PROSITE is copyright. It is produced by the SIB Swiss Institute
Bioinformatics. There are no restrictions on its use by non-profit
institutions as long as its content is in no way modified. Usage by and
for commercial entities requires a license agreement. For information
about the licensing scheme send an email to
or see: prosite_license.html.