Catalyzes the conversion of cystathionine to cysteine, and homocysteine to sulfide.

MNKKTKLIHGGHTTDDYTGAVTTPIYQTSTYLQDDIGDLRQGYEYSRTANPTRSSVESVI ATLENGKHGFAFSSGVAAISAVVMLLDKGDHIILNSDVYGGTYRALTKVFTRFGIEVDFV DTTHTDSIVQAIRPTTKMLFIETPSNPLLRVTDIKKSAEIAKEHGLISVVDNTFMTPYYQ NPLDLGIDIVLHSATKYLGGHSDVVAGLVATSDDKLAERLAFISNSTGGILGPQDSYLLV RGIKTLGLRMEQINRSVIEIIKMLQAHPAVQQVFHPSIESHLNHDVHMAQADGHTGVIAF EVKNTESAKQLIKATSYYTLAESLGAVESLISVPALMTHASIPADIRAKEGITDGLVRIS VGIEDTEDLVDDLKQALDTL 387

	PMID	Title & Author	Abstract	Year
0	17056751	Conversion of methionine to cysteine in Bacillus subtilis and its regulation. Marie-Françoise Hullo , Sandrine Auger, Olga Soutourina, Octavian Barzu, Mireille Yvon, Antoine Danchin, Isabelle Martin-Verstraete	Bacillus subtilis can use methionine as the sole sulfur source, indicating an efficient conversion of methionine to cysteine. To characterize this pathway, the enzymatic activities of CysK, YrhA and YrhB purified in Escherichia coli were tested. Both CysK and YrhA have an O-acetylserine-thiol-lyase activity, but YrhA was 75-fold less active than CysK. An atypical cystathionine beta-synthase activity using O-acetylserine and homocysteine as substrates was observed for YrhA but not for CysK. The YrhB protein had both cystathionine lyase and homocysteine gamma-lyase activities in vitro. Due to their activity, we propose that YrhA and YrhB should be renamed MccA and MccB for methionine-to-cysteine conversion. Mutants inactivated for cysK or yrhB grew similarly to the wild-type strain in the presence of methionine. In contrast, the growth of an DeltayrhA mutant or a luxS mutant, inactivated for the S-ribosyl-homocysteinase step of the S-adenosylmethionine recycling pathway, was strongly reduced with methionine, whereas a DeltayrhA DeltacysK or cysE mutant did not grow at all under the same conditions. The yrhB and yrhA genes form an operon together with yrrT, mtnN, and yrhC. The expression of the yrrT operon was repressed in the presence of sulfate or cysteine. Both purified CysK and CymR, the global repressor of cysteine metabolism, were required to observe the formation of a protein-DNA complex with the yrrT promoter region in gel-shift experiments. The addition of O-acetyl-serine prevented the formation of this protein-DNA complex.	2007
1	18812398	S-box and T-box riboswitches and antisense RNA control a sulfur metabolic operon of Clostridium acetobutylicum. Gaëlle André , Sergine Even, Harald Putzer, Pierre Burguière, Christian Croux, Antoine Danchin, Isabelle Martin-Verstraete, Olga Soutourina	The ubiGmccBA operon of Clostridium acetobutylicum is involved in methionine to cysteine conversion. We showed that its expression is controlled by a complex regulatory system combining several RNA-based mechanisms. Two functional convergent promoters associated with transcriptional antitermination systems, a cysteine-specific T-box and an S-box riboswitch, are located upstream of and downstream from the ubiG operon, respectively. Several antisense RNAs were synthesized from the downstream S-box-dependent promoter, resulting in modulation of the level of ubiG transcript and of MccB activity. In contrast, the upstream T-box system did not appear to play a major role in regulation, leaving antisense transcription as the major regulatory mechanism for the ubiG operon. The abundance of sense and antisense transcripts was inversely correlated with the sulfur source availability. Deletion of the downstream promoter region completely abolished the sulfur-dependent control of the ubiG operon, and the expression of antisense transcripts in trans did not restore the regulation of the operon. Our data revealed important insights into the molecular mechanism of cis-antisense-mediated regulation, a control system only rarely observed in prokaryotes. We proposed a regulatory model in which the antisense RNA controlled the expression of the ubiG operon in cis via transcriptional interference at the ubiG locus.	2008

Hullo M F , Auger S , Soutourina O , et al. Conversion of Methionine to Cysteine in Bacillus subtilis and Its Regulation[J]. Journal of Bacteriology, 2007, 189(1):187-197.