Transducing particles of Staphylococcus aureus pathogenicity island SaPI1 are comprised of helper phage-encoded proteins

The relationship between the composition of SaPI1 transducing particles and those of helper phage 80 alpha was 14 investigated by direct comparison of virion proteins. Twelve virion proteins were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry; all were present in both 80 alpha and SaPI1 virions, and all were encoded by 80 alpha. No SaPI1-encoded proteins were detected. This confirms the prediction that SaPH is encapsidated in a virion assembled from helper phage-encoded proteins.