Characterization of the 48.5 kDa chorionic gonadotropin-like protein from Xanthomonas maltophilia.

Our laboratory has previously reported the isolation of a 48.5 kDa membrane protein from Xanthomonas maltophilia (ATCC 13637) which immunologically cross-reacts with the beta-subunit of human chorionic gonadotropin (hCG) in both polyclonal and monoclonal radioimmunoassays (RIA) (1). The protein showed no reaction in RIAs for human LH, TSH, or the free alpha subunit of hCG. We have now improved the protein purification procedure and have obtained adequate bacterial protein to characterize the pure protein (designated xCG) in RIAs and also to obtain amino acid composition and partial sequence. We present these data and compare homology to hCG. An RIA for the bacterial protein has also been developed.