The tailspike protein of Shigella phage Sf6 - A structural homolog of Salmonella phage p22 tailspike protein without sequence similarity in the beta-helix domain

Item Type:	Article
Title:	The tailspike protein of Shigella phage Sf6 - A structural homolog of Salmonella phage p22 tailspike protein without sequence similarity in the beta-helix domain
Creators Name:	Freiberg, A. and Morona, R. and Van den Bosch, L. and Jung, C. and Behlke, J. and Carlin, N. and Seckler, R. and Baxa, U.
Abstract:	Bacteriophage Sf6 tailspike protein is functionally equivalent to the well characterized tailspike of Salmonella phage P22, mediating attachment of the viral particle to host cell-surface polysaccharide. However, there is significant sequence similarity between the two 70-kDa polypeptides only in the N-terminal putative capsid-binding domains. The major, central part of P22 tail-spike protein, which forms a parallel β-helix and is responsible for saccharide binding and hydrolysis, lacks detectable sequence homology to the Sf6 protein. After recombinant expression in Escherichia coli as a soluble protein, the Sf6 protein was purified to homogeneity. As shown by circular dichroism and Fourier transform infrared spectroscopy, the secondary structure contents of Sf6 and P22 tailspike proteins are very similar. Both tailspikes are thermostable homotrimers and resist denaturation by SDS at room temperature. The specific endorhamnosidase activities of Sf6 tailspike protein toward fluorescence-labeled dodeca-, deca-, and octasaccharide fragments of Shigella O-antigen suggest a similar active site topology of both proteins. Upon deletion of the N-terminal putative capsid-binding domain, the protein still forms a thermostable, SDS-resistant trimer that has been crystallized. The observations strongly suggest that the tailspike of phage Sf6 is a trimeric parallel {beta}-helix protein with high structural similarity to its functional homolog from phage P22.
Keywords:	Amino Acid Sequence, Bacteriophage P22, Base Sequence, Circular Dichroism, DNA Primers, Fourier Transform Infrared Spectroscopy, Glycoside Hydrolases, Molecular Cloning, Molecular Sequence Data, Polyacrylamide Gel Electrophoresis, Secondary Protein Structure, Shigella, Viral Tail Proteins
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	278
Number:	3
Page Range:	1542-1548
Date:	17 January 2003
Official Publication:	https://doi.org/10.1074/jbc.M205294200
PubMed:	View item in PubMed

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