Enzymic and molecular properties of base-plate parts of bacteriophage P22.
Using 14C-labeled Salmonella bacterial cells as the substrate, the enzymic and molecular properties of the base-plate parts of phage P22 were studied. The base-plate part consisted of a single protein species which cleaved extensively the O-antigen of Salmonella typhimurium, Salmonelly schottmuellerie and with somewhat slower rate that of Salmonella typhi, releasing oligo-saccharide products with rhamnose at the reducing end. Much less cleavage was observed with a strain of S. typhimurium lysogenic for P22, and no significant reaction with Salmonella anatum, Salmonella newington and Salmonella minneapolis. The base-plate part enzyme was a very heat-stable protein and only 10-20% loss was observed after treatment at 85 degrees C for 5 min. The pH optimum of the enzyme was around 7.5, and the glycosidase activity was not influenced by the ionic strength (25-250 mM( of the medium or the presence of Mg2+. The molecular weight of the base-plate part was 320,000 by sedimentation equilibrium. Dodecylsulphate-acrylamide gel electrophoresis revealed a single band of molecular weight 77,000, indicating that a single base-plate part corresponds to a tetramer of identical subunits. Circular dichroism spectra of P22 base-plate parts showed a major contribution of beta structure. The protein was rich in acidic amino acids, glycine and serine.
D000596:Amino Acids / Q000032:analysis; D000941:Antigens; D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D009994:Osmolar Concentration; D010447:Peptide Hydrolases / Q000378:metabolism; D012475:Salmonella / Q000378:metabolism*; D012483:Salmonella Phages / Q000378:metabolism* / Q000648:ultrastructure; D012486:Salmonella typhimurium / Q000378:metabolism; D013045:Species Specificity; D013696:Temperature; D014764:Viral Proteins / Q000378:metabolism*
D000596:Amino Acids; D000941:Antigens; D014764:Viral Proteins; D010447:Peptide Hydrolases