Protein Family Models

A single molecule of H protein is found on each of the 12 spikes on the microvirus shell. H is involved in the ejection of the phage DNA, and at least one copy is injected into the host's periplasmic space along with the ssDNA viral genome [1]. Part of H is thought to lie outside the shell, where it recognises lipopolysaccharide from virus-sensitive strains [2]. Part of H may lie within the capsid, since mutations in H can influence the DNA ejection mechanism by affecting the DNA-protein interactions [3]. H may span the capsid through the hydrophilic channels formed by G proteins [1]. Elucidation of the DNA-ejection mechanism from the crystal structure of part of the H protein shows that this tail-less icosahedral, single-stranded DNA phiX174-like coliphage bacteriophage requires H as a pilot protein for its DNA-delivery. H oligomerises to form a tube the function of which seems to be the delivery of the DNA genome across the host's periplasmic space into the host cytoplasm. The tube is constructed of ten alpha-helices with their amino termini arrayed in a right-handed super-helical coiled-coil and their carboxy termini arrayed in a left-handed super-helical coiled-coil. The tube spans the periplasmic space and is present while the genome is being delivered into the host cell's cytoplasm [4]. [1]. 8158636. Analysis of the single-stranded DNA bacteriophage phi X174,. refined at a resolution of 3.0 A.. McKenna R, Ilag LL, Rossmann MG;. J Mol Biol 1994;237:517-543.. [2]. 10225278. Specific interaction of fused H protein of bacteriophage phiX174. with receptor lipopolysaccharides.. Suzuki R, Inagaki M, Karita S, Kawaura T, . TRUNCATED at 1650 bytes (from Pfam)

Date:

2024-08-14

Date:

2019-09-10