EFFECT OF VIBRIO-CHOLERAE NON-O1 PROTEASE ON LYSOZYME, LACTOFERRIN AND SECRETORY IMMUNOGLOBULIN-A

The effect of Vibrio cholerae non-O1 protease on host defense proteins (lysozyme, secretory immunoglobulin A and lactoferrin) was studied in relation to its virulence mechanism. The proteins treated with the pr otease were analysed by SDS-PAGE. There was no influence of the protea se on lysozyme. The protease cleaved lactoferrin into two fragments of 50 kDa and 34 kDa. N-terminal amino acid sequencing of these fragment s revealed that the cleavage site was near the hinge region, between s erine 420 and serine 421. This cleavage could affect the transition fr om open to closed configuration which is involved in iron binding and release. The anti-bacterial activity of lactoferrin was not affected b y protease treatment. Secretory immunoglobulin A yielded a 42-kDa prot ein as the cleavage product. The susceptibility of secretory immunoglo bulin A to V. cholerae non-O1 protease suggests a mechanism by which b acteria might evade the effect of this immunoglobulin.