The fourth component of the sarcoglycan complex

We found a novel dystrophin-associated protein (DAP) exhibiting almost the same mobility as gamma-sarcoglycan on SDS-PAGE. This novel DAP with basic charge is separated from gamma-sarcoglycan by 2-dimensional PAGE or de-N-glycosylation followed by SDS-PAGE. This DAP is most likely the rabbit homologue of "delta-sarcoglycan", the gamma-sarcoglycan-like protein identified previously [Nigro et al. (1996) Hum. Mol. Genet. 5, 1179-1186], since an internal amino acid sequence from the DAP matched the predicted amino acid sequence of "human delta-sarcoglycan" within the limits of species difference and this DAP was recognized by anti-"delta-sarcoglycan" antibody. The DAP was found to be contained in the sarcoglycan fraction which was prepared by treatment of the dystrophin-DAP complex with n-octyl beta-D-glucoside and crosslinked with beta- and/or gamma-sarcoglycan by a chemical crosslinker, dithiobis(succinimidyl propionate). Therefore, we concluded that the DAP is the fourth component of the sarcoglycan complex.