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Structure of the aliphatic sulfonate-binding protein SsuA from Escherichia coli.

ABSTRACT: Sulfur is an essential component for the biosynthesis of the sulfur-containing amino acids L-methionine and L-cysteine. Under sulfur-starvation conditions, bacteria are capable of scavenging sulfur from sulfur-containing compounds and transporting it across membranes. Here, the crystal structure of the periplasmic aliphatic sulfonate-binding protein SsuA from Escherichia coli is reported at 1.75 A resolution in the substrate-free state. The overall structure of SsuA resembles the structures of other periplasmic binding proteins and contains two globular domains that form a cleft. Comparison with other periplasmic binding proteins revealed that one of the domains has been displaced by a rigid movement of 17 degrees . Interestingly, the tight crystal packing appears to be mediated by a 13-amino-acid tail from the cloning that folds within the cleft of the next monomer.

SUBMITTER: Beale J

PROVIDER: S-EPMC2852328 | biostudies-literature | 2010 Apr

REPOSITORIES: biostudies-literature

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Structure of the aliphatic sulfonate-binding protein SsuA from Escherichia coli.

Beale John J Lee Sang Yun SY Iwata So S Beis Konstantinos K

Acta crystallographica. Section F, Structural biology and crystallization communications 20100326 Pt 4

Sulfur is an essential component for the biosynthesis of the sulfur-containing amino acids L-methionine and L-cysteine. Under sulfur-starvation conditions, bacteria are capable of scavenging sulfur from sulfur-containing compounds and transporting it across membranes. Here, the crystal structure of the periplasmic aliphatic sulfonate-binding protein SsuA from Escherichia coli is reported at 1.75 A resolution in the substrate-free state. The overall structure of SsuA resembles the structures of o ...[more]

PMID: 20383006

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Project description:For many pathogenic microorganisms, iron acquisition from host heme sources stimulates growth, multiplication, ultimately enabling successful survival and colonization. In gram-negative Escherichia coli O157:H7, Shigella dysenteriae and Yersinia enterocolitica the genes encoded within the heme utilization operon enable the effective uptake and utilization of heme as an iron source. While the complement of proteins responsible for heme internalization has been determined in these organisms, the fate of heme once it has reached the cytoplasm has only recently begun to be resolved. Here we report the first crystal structure of ChuX, a member of the conserved heme utilization operon from pathogenic E. coli O157:H7 determined at 2.05 A resolution. ChuX forms a dimer which remarkably given low sequence homology, displays a very similar fold to the monomer structure of ChuS and HemS, two other heme utilization proteins. Absorption spectral analysis of heme reconstituted ChuX demonstrates that ChuX binds heme in a 1:1 manner implying that each ChuX homodimer has the potential to coordinate two heme molecules in contrast to ChuS and HemS where only one heme molecule is bound. Resonance Raman spectroscopy indicates that the heme of ferric ChuX is composed of a mixture of coordination states: 5-coordinate and high-spin, 6-coordinate and low-spin, and 6-coordinate and high-spin. In contrast, the reduced ferrous form displays mainly a 5-coordinate and high-spin state with a minor contribution from a 6-coordinate and low-spin state. The nu(Fe-CO) and nu(C-O) frequencies of ChuX-bound CO fall on the correlation line expected for histidine-coordinated hemoproteins indicating that the fifth axial ligand of the ferrous heme is the imidazole ring of a histidine residue. Based on sequence and structural comparisons, we designed a number of site-directed mutations in ChuX to probe the heme binding sites and dimer interface. Spectral analysis of ChuX and mutants suggests involvement of H65 and H98 in heme coordination as mutations of both residues were required to abolish the formation of the hexacoordination state of heme-bound ChuX.

Dataset Information

Structure of the aliphatic sulfonate-binding protein SsuA from Escherichia coli.

Publications

Structure of the aliphatic sulfonate-binding protein SsuA from Escherichia coli.

Similar Datasets

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