Electrophoretic characterization of a novel cysteine protease produced by Vibrio harveyi

Electrophoretic characterization of a novel cysteine protease produced by pathogenic luminous Vibrio harveyi, originally isolated from diseased tiger prawn Penaeus monodon in Taiwan, is demonstrated in the present study using native polyacrylamide gel electrophoresis (native PAGE), sodium dodecyl sulfate-PAGE (SDS-PAGE), crossed immunoelectrophoresis (CIE) and isoelectric focusing (IEF) gels. The protease has a pI of 6.4 and exhibits a fast-migrating feature in native-PAGE and CIE gels indicating that it is a negatively charged protease. The protease electrophoresed as a 22 kDa protein band in native- and SDS-PAGE (in SDS - buffer with or without the presence of 2-mercaptoethanol) while it electrophoresed as a 38 kDa protein band in SDS-PAGE when the samples were boiled for 10 min prior to electrophoresis. The results reveal that the enzyme is an SDS-resistant monomeric protease and its high negative charge is not influenced by SDS (detergent) without boiling the sample. The present results are useful in determining proteins of similar nature to this unique cysteine protease.