6C3Z

T477A SiRHP

Summary for 6C3Z

• Entry DOI: 10.2210/pdb6c3z/pdb
• Related: 6C3M 6C3X 6C3Y
• Descriptor: Sulfite reductase [NADPH] hemoprotein beta-component, PHOSPHATE ION, POTASSIUM ION, ... (6 entities in total)
• Functional Keywords: redox, iron-sulfur cluster, fe4-s4 cluster, siroheme, iron, metal binding protein
• Biological source: Escherichia coli (strain K12)
• Total number of polymer chains: 1
• Total formula weight: 65463.44

Authors

Stroupe, M.E. (deposition date: 2018-01-11, release date: 2018-06-13, Last modification date: 2023-12-27)

Primary citation

Cepeda, M.R.,McGarry, L.,Pennington, J.M.,Krzystek, J.,Stroupe, M.E.
The role of extended Fe4S4cluster ligands in mediating sulfite reductase hemoprotein activity.
Biochim. Biophys. Acta, 1866:933-940, 2018

PubMed Abstract: 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 FeS 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 FeS 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.

PubMed: 29852252
DOI: 10.1016/j.bbapap.2018.05.013

Experimental method

X-RAY DIFFRACTION (1.681 Å)