Dataset Information

Crystal structure of the read-through domain from bacteriophage Q? A1 protein.

ABSTRACT: Bacteriophage Q? is a small RNA virus that infects Escherichia coli. The virus particle contains a few copies of the minor coat protein A1, a C-terminally prolonged version of the coat protein, which is formed when ribosomes occasionally read-through the leaky stop codon of the coat protein. The crystal structure of the read-through domain from bacteriophage Q? A1 protein was determined at a resolution of 1.8 Å. The domain consists of a heavily deformed five-stranded ?-barrel on one side of the protein and a ?-hairpin and a three-stranded ?-sheet on the other. Several short helices and well-ordered loops are also present throughout the protein. The N-terminal part of the read-through domain contains a prominent polyproline type II helix. The overall fold of the domain is not similar to any published structure in the Protein Data Bank.

SUBMITTER: Rumnieks J

PROVIDER: S-EPMC3218364 | biostudies-literature | 2011 Oct

REPOSITORIES: biostudies-literature

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Crystal structure of the read-through domain from bacteriophage Qβ A1 protein.

Rumnieks Janis J Tars Kaspars K

Protein science : a publication of the Protein Society 20110818 10

Bacteriophage Qβ is a small RNA virus that infects Escherichia coli. The virus particle contains a few copies of the minor coat protein A1, a C-terminally prolonged version of the coat protein, which is formed when ribosomes occasionally read-through the leaky stop codon of the coat protein. The crystal structure of the read-through domain from bacteriophage Qβ A1 protein was determined at a resolution of 1.8 Å. The domain consists of a heavily deformed five-stranded β-barrel on one side of the ...[more]

PMID: 21805520

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Project description:BACKGROUND: Bacteriophages encode endolysins to lyse their host cell and allow escape of their progeny. Endolysins are also active against Gram-positive bacteria when applied from the outside and are thus attractive anti-bacterial agents. LysK, an endolysin from staphylococcal phage K, contains an N-terminal cysteine-histidine dependent amido-hydrolase/peptidase domain (CHAP(K)), a central amidase domain and a C-terminal SH3b cell wall-binding domain. CHAP(K) cleaves bacterial peptidoglycan between the tetra-peptide stem and the penta-glycine bridge. METHODS: The CHAP(K) domain of LysK was crystallized and high-resolution diffraction data was collected both from a native protein crystal and a methylmercury chloride derivatized crystal. The anomalous signal contained in the derivative data allowed the location of heavy atom sites and phase determination. The resulting structures were completed, refined and analyzed. The presence of calcium and zinc ions in the structure was confirmed by X-ray fluorescence emission spectroscopy. Zymogram analysis was performed on the enzyme and selected site-directed mutants. RESULTS: The structure of CHAP(K) revealed a papain-like topology with a hydrophobic cleft, where the catalytic triad is located. Ordered buffer molecules present in this groove may mimic the peptidoglycan substrate. When compared to previously solved CHAP domains, CHAP(K) contains an additional lobe in its N-terminal domain, with a structural calcium ion, coordinated by residues Asp45, Asp47, Tyr49, His51 and Asp56. The presence of a zinc ion in the active site was also apparent, coordinated by the catalytic residue Cys54 and a possible substrate analogue. Site-directed mutagenesis was used to demonstrate that residues involved in calcium binding and of the proposed active site were important for enzyme activity. CONCLUSIONS: The high-resolution structure of the CHAP(K) domain of LysK was determined, suggesting the location of the active site, the substrate-binding groove and revealing the presence of a structurally important calcium ion. A zinc ion was found more loosely bound. Based on the structure, we propose a possible reaction mechanism. Future studies will be aimed at co-crystallizing CHAP(K) with substrate analogues and elucidating its role in the complete LysK protein. This, in turn, may lead to the design of site-directed mutants with altered activity or substrate specificity.

Dataset Information

Crystal structure of the read-through domain from bacteriophage Q? A1 protein.

Publications

Crystal structure of the read-through domain from bacteriophage Qβ A1 protein.

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