title: A localized surface protein of guinea pig sperm exhibits free diffusion in its domain.
abstract: Using the technique of fluorescence redistribution after photobleaching, we are studying the cellular mechanisms involved in localizing surface molecules to particular domains. A number of antigens localized to discrete surface regions have been identified with monoclonal antibodies on guinea pig sperm cells ( Primakoff , P., and D. G. Myles , 1983, Dev. Biol., 98:417-428). One of these monoclonal antibodies, PT-1, binds exclusively to the posterior tail region of the sperm cell surface. PT-1 recognizes an integral membrane protein that in complex with n-octyl-beta-D-glucopyranoside has a sedimentation coefficient of 6.8S in sucrose density gradients. Fluorescence redistribution after photobleaching measurements reveal that within its surface domain the PT-1 antigen diffuses rapidly (D = 2.5 X 10(-9) cm2/s) and completely (greater than 90% recovery after bleaching). These results rule out for this membrane protein all models that invoke immobilization as a mechanism for maintaining localization. We propose that the mechanism for localization of the PT-1 antigen may be a barrier to diffusion at the domain boundary.
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000032:analysis; D002451:Cell Compartmentation; D004058:Diffusion; D006168:Guinea Pigs; D008297:Male; D008560:Membrane Fluidity; D008565:Membrane Proteins / Q000502:physiology*; D013082:Sperm Tail / Q000648:ultrastructure; D013094:Spermatozoa / Q000502:physiology / Q000648:ultrastructure*
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D008565:Membrane Proteins