The N-terminal Domain of Escherichia coli Assimilatory NADPH-Sulfite Reductase Hemoprotein Is an Oligomerization Domain That Mediates Holoenzyme Assembly.

ABSTRACT: Assimilatory NADPH-sulfite reductase (SiR) from Escherichia coli is a structurally complex oxidoreductase that catalyzes the six-electron reduction of sulfite to sulfide. Two subunits, one a flavin-binding flavoprotein (SiRFP, the α subunit) and the other an iron-containing hemoprotein (SiRHP, the β subunit), assemble to make a holoenzyme of about 800 kDa. How the two subunits assemble is not known. The iron-rich cofactors in SiRHP are unique because they are a covalent arrangement of a Fe4S4 cluster attached through a cysteine ligand to an iron-containing porphyrinoid called siroheme. The link between cofactor biogenesis and SiR stability is also ill-defined. By use of hydrogen/deuterium exchange and biochemical analysis, we show that the α8β4 SiR holoenzyme assembles through the N termin

SUBMITTER: Askenasy I 

PROVIDER: S-EPMC4521050 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature