4osd | pdb_00004osd
Dimer of a C-terminal fragment of phage T4 gp5 beta-helix
Structural highlights
FunctionNEEDL_BPT4 Tail-associated lysozyme of the baseplate hub that is essential for localized hydrolysis of bacterial cell wall necessary for viral DNA injection. The needle-like gp5 protein punctures the outer cell membrane and then digests the peptidoglycan cell wall in the periplasmic space. Involved in the tail assembly.[1] [2] Publication Abstract from PubMedGene product 5 (gp5) of bacteriophage T4 is a spike-shaped protein that functions to disrupt the membrane of the target cell during phage infection. Its C-terminal domain is a long and slender beta-helix that is formed by three polypeptide chains wrapped around a common symmetry axis akin to three interdigitated corkscrews. The folding and biophysical properties of such triple-stranded beta-helices, which are topologically related to amyloid fibers, represent an unsolved biophysical problem. Here, we report structural and biophysical characterization of T4 gp5 beta-helix and its truncated mutants of different lengths. A soluble fragment that forms a dimer of trimers and that could comprise a minimal self-folding unit has been identified. Surprisingly, the hydrophobic core of the beta-helix is small. It is located near the C-terminal end of the beta-helix and contains a centrally positioned and hydrated magnesium ion. A large part of the beta-helix interior comprises a large elongated cavity that binds palmitic, stearic, and oleic acids in an extended conformation suggesting that these molecules might participate in the folding of the complete beta-helix. Structure and Biophysical Properties of a Triple-Stranded Beta-Helix Comprising the Central Spike of Bacteriophage T4.,Buth SA, Menin L, Shneider MM, Engel J, Boudko SP, Leiman PG Viruses. 2015 Aug 18;7(8):4676-706. doi: 10.3390/v7082839. PMID:26295253[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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