Details

Autor(en) / Beteiligte

• Cepeda, Marisa R
• McGarry, Lauren
• Pennington, Joseph M
• Krzystek, J
• Stroupe, M Elizabeth

Titel

The role of extended Fe 4 S 4 cluster ligands in mediating sulfite reductase hemoprotein activity

Ist Teil von

• Biochimica et biophysica acta. Proteins and proteomics, 2018-09, Vol.1866 (9), p.933

Ort / Verlag

Netherlands: Elsevier

Erscheinungsjahr

2018

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The siroheme-containing subunit from the multimeric hemoflavoprotein NADPH-dependent sulfite reductase (SiR/SiRHP) catalyzes the six electron-reduction of SO to S . Siroheme is an iron-containing isobacteriochlorin that is found in sulfite and homologous siroheme-containing nitrite reductases. Siroheme does not work alone but is covalently coupled to a Fe S cluster through one of the cluster's ligands. One long-standing hypothesis predicted from this observation is that the environment of one iron-containing cofactor influences the properties of the other. We tested this hypothesis by identifying three amino acids (F437, M444, and T477) that interact with the Fe S cluster and probing the effect of altering them to alanine on the function and structure of the resulting enzymes by use of activity assays, X-ray crystallographic analysis, and EPR spectroscopy. We showed that F437 and M444 gate access for electron transfer to the siroheme-cluster assembly and the direct hydrogen bond between T477 and one of the cluster sulfides is important for determining the geometry of the siroheme active site.