Studies in FY'93 on structure and function of gonococcal surface components were continuations of previously-initiated attempts to describe biological behaviors of these organisms to the physicochemical attributes of their surfaces. Earlier results on electrophoretic characteristics of whole gonococci established that both lipooligosaccharide (Los) and Opa outer membrane proteins exert individual an collective influences on cell surface charge. Some Opa proteins contribute positive charge on whole gonococci. Other Opa proteins greatly enhanced negativity in spite of their having abundant cationic amino acids in their (predicted) surface- exposed portions. This affect was shown to result from accretion of polyanions (such as DNA and sulfated polysaccharide) on cells that expressed certain Opa proteins. These Opa+ gonococci, in effect, acquire a """"""""garbage"""""""" capsule. Most recent studies examined the effects of piliation on gonococcal surface charge and behavior. The results show that pilus+ cells are less negatively charged than their pilus counterparts. Piliation 'dampens' influences of LOS and Opa on cell charge, with pilus+ cells maintaining a net charge near zero, often slightly positive, regardless of the environment or which outer membrane components they express. Variant pilus+ organisms that synthesize different pilin subunits differ in both their electrophoretic mobilities and their comparative adherences to eukaryotic cells, but EPM correlates imperfectly with adherence levels. If pilus+ LoSb Opal cells are sialylated, their EPM is shifted to very negative values. Similar phenomena accompany sialylation of OpaC cells; when these variants are unsialylated, they bind DNA, but DNA no longer binds when the cells have been sialylated. In contrast OpaA+ variants bind DNA whether or not their LOS is sialylated. These phenomena reinforce other data suggestive that these two Opa proteins are quite differently disposed on the 'gonococcus' surface.
