Heat-modifiable outer membrane proteins of Neisseria meningitidis and their organization within the membrane

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Abstract
N. meningitidis group B serotype 2 strain M986 contains 2 predominant outer membrane proteins, with apparent MW of 41,000 (protein b) and 28,000 (protein e). Heating of outer membrane vesicles at 56.degree. C for 1 min in the presence of sodium dodecyl sulfate (SDS) and urea caused protein b to migrate as a high MW aggregate (MW, about 130,000), designated b**, and protein e to migrate with a lower apparent MW (21,000), designated e*. Thus, 2 classes of heat-modifiable proteins are present in the outer membrane of N. meningitidis. These shifts in MW were confirmed by a 2-dimensional SDS-polyacrylamide gel electrophoresis technique in which the proteins are run in the 1st dimension after incubation in SDS at 56.degree. C, and then in the 2nd dimension after heating the 1st-dimensional gel at 100.degree. C. Heating the outer membrane in SDS at 56.degree. C for 20 min caused much of b** to disaggregate and denature into b (41,000 daltons). In contrast, protein e could be rapidly solubilized by SDS at room temperature into its monomeric state (e*), but it was not converted to its final higher apparent MW of 28,000 (e) unless heated at 100.degree. C for 2 min. Apparently, protein b exists in the membrane as trimers or tetramers in a transmembrane configuration and protein e exists as subunits on the exterior surface of the outer membrane and has a highly ordered tertiary structure.