Cysteine-Persulfide Sulfane Sulfur-Ligated Zn Complex of Sulfur-Carrying SufU in the SufCDSUB System for Fe-S Cluster Biosynthesis.

SufU, a component of the SufCDSUB Fe-S cluster biosynthetic system, serves as a Zn-dependent sulfur-carrying protein that delivers inorganic sulfur in the form of cysteine persulfide from SufS to SufBCD. To understand this sulfur delivery mechanism, we studied the X-ray crystal structure of SufU and its sulfur-carrying state (persulfurated SufU) and performed functional analysis of the conserved amino acid residues around the Zn sites. Interestingly, sulfur-carrying SufU with Cys41-persulfide (Cys41-S-S) exhibited a unique Zn coordination structure, in which electrophilic S is ligated to Zn and nucleophilic/anionic S is bound to distally conserved Arg125.

A capsule-associated gene of , , is involved in pH homeostasis.

The gene is known to be involved in capsule formation in the basidiomycete yeast . A null mutant of , Δ, lacks a capsule around the cell wall and its acidic organelles are not stained with quinacrine. In order to clarify whether the Cap64 protein indeed maintains vacuole or vesicle acidification, so that the vesicle containing the capsule polysaccharide or DBB substrate are transported to the cell membrane side, the relationship between and intracellular transport genes and between and enzyme-secretion activity were analysed.

Structure of sirohydrochlorin ferrochelatase SirB: the last of the structures of the class II chelatase family.

The crystal structure of Bacillus subtilis SirB, which catalyses the insertion of Fe2+ into the substrate sirohydrochlorin (SHC) in siroheme biosynthesis, is reported herein as the last of the structures of class II chelatases. The structure of SirB with Co2+ showed that the active site of SirB is located at the N-terminal domain with metal-binding amino acid residues His10, Glu43, and His76, which was also predicted for CbiX, but is distinct from the C-terminal active sites of CbiK and HemH. The biosynthetic model reactions using SirB, Co2+ and uroporphyrin I or protoporphyrin IX as a SHC analogue revealed that SirB showed chelatase activity for uroporphyrin I, but not for protoporphyrin IX.