Isolation of a surface glycoprotein from Myxococcus xanthus

Abstract

The isolation of a glycoprotein from vegetative cells of Myxococcus xanthus is reported. The protein, abbreviated VGP, was first identified during a survey of surface proteins as a major protein that could be radioiodinated in vegetative, but not developing, cells (P.Y. Maeba, J. Bacteriol. 155:1033-1041, 1983). The protein was extracted from membranes with Triton X-100 and subsequently purified by DEAE-cellulose chromatography, chromatofocusing, and gel filtration. The protein has an Mr of approximately 74,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an isoelectric point of 3.2 to 3.3. The carbohydrate moiety which made up approximately 13.5% of the weight of the VGP comprised primarily neutral sugars and smaller amounts of hexosamines and uronic acids. The amino acid content revealed no unusual features, but analysis by the method of Barrantes (F. Barrantes, Biochem. Biophys. Res. Commun. 62:407-414, 1975) indicated it is likely a peripheral membrane protein. The protein makes up approximately 1% of the total cell protein and is a prominent surface structure. Because glycoproteins have been implicated in cellular interactions in a number of systems, the VGP may play an important role in the social behavior exhibited by M. xanthus.