Neisseria gonorrhoeae IgA protease. Secretion and implications for pathogenesis.

A cloned 5 kb DNA fragment from Neisseria gonorrhoeae strain MS11 promotes expression and excretion of IgA protease in E. coli and other Gram-negative hosts. DNA sequencing reveals a large open reading frame coding for a precursor molecule of 169 kd. The 106 kd mature IgA protease is released from the bacteria in conjunction with a 15 kd soluble precursor segment, the alpha-protein. In contrast, the carboxy terminal portion of the precursor, the beta-protein (45 kd), remains associated with the outer bacterial membrane. The three proteins result form autoproteolytic cleavage at sites in the precursor which are similar to the target site in IgA1. Consensus sequences of the specific cleavage sites are found in a number of relevant human proteins. IgA protease may therefore have other natural substrates besides IgA1. The soluble alpha-protein as well as the membrane bound beta-protein, both associated with IgA protease, may confer additional virulence functions to the gonococcus.