The "rhodanese" fold and catalytic mechanism of 3-mercaptopyruvate sulfurtransferases: crystal structure of SseA from Escherichia coli.
3-Mercaptopyruvate sulfurtransferases (MSTs) catalyze, in vitro, the transfer of a sulfur atom from substrate to cyanide, yielding pyruvate and thiocyanate as products. They display clear structural homology with the protein fold observed in the rhodanese sulfurtransferase family, composed of two structurally related domains. The role of MSTs in vivo, as well as their detailed molecular mechanisms of action have been little investigated. Here, we report the crystal structure of SseA, a MST from Escherichia coli, which is the first MST three-dimensional structure disclosed to date. SseA displays specific structural differences relative to eukaryotic and prokaryotic rhodaneses. In particular, conformational variation of the rhodanese active site loop, hosting the family invariant catalytic Cys residue, may support a new sulfur transfer mechanism involving Cys237 as the nucleophilic species and His66, Arg102 and Asp262 as residues assisting catalysis.
Spallarossa
Andrea
A
Dipartimento di Fisica-INFM, Centro di Eccellenza per la Ricerca Biomedica, Universita' di Genova; Via Dodecaneso 33, 16146 Genoa, Italy.
Forlani
Fabio
F
Carpen
Aristodemo
A
Armirotti
Andrea
A
Pagani
Silvia
S
Bolognesi
Martino
M
Bordo
Domenico
D
D000595:Amino Acid Sequence; D001665:Binding Sites / Q000502:physiology; D002384:Catalysis; D003545:Cysteine / Q000737:chemistry; D004926:Escherichia coli / Q000201:enzymology*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017510:Protein Folding; D017386:Sequence Homology, Amino Acid; D013455:Sulfur / Q000378:metabolism; D013466:Sulfurtransferases / Q000737:chemistry* / Q000378:metabolism; D013884:Thiosulfate Sulfurtransferase / Q000737:chemistry*
D013455:Sulfur; D013466:Sulfurtransferases; D013884:Thiosulfate Sulfurtransferase; C021550:3-mercaptopyruvate sulphurtransferase; D003545:Cysteine