Electrophoretic characterisation of the major cat parotid salivary protein Original Research Article

High resolution electrophoretic analysis of cat parotid saliva indicates that the major cat parotid salivary protein (MCPSP) exists in a monomeric form (Mr 30 000) and a dimeric form (Mr 60 000). The MCPSP monomers are non-covalently linked in the dimer which shows an atypical resistance to dissociation upon sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) under non-reducing conditions. Two-dimensional electrophoresis (2-DE) indicates that the MCPSP consists of a complex cluster of spots indicative of charge and size microheterogeneity. Neuraminidase treatment indicates that the charge differences are unrelated to sialisation but carbamylation has a pronounced effect consistent with chemical modification of multiple lysine ϵ-amino groups. The application of Multiphor® 2-DE to cat saliva is problematic as a major proportion of the MCPSP appears in the dimeric rather than the desired monomeric form.