This award will allow continuation of a scientific collabo- ration between the Biochemistry Departments of the University of Maryland at Baltimore and the Federal University of Rio de Janeiro. The investigators are Guiseppi Inesi (U.S.) and Leopoldo deMeis (Brazil). The research is aimed at a clarification of the mechanism of ATP dependent calcium transport across biological membranes. The experimental system will consist of membrane vesicles derived from sarcoplasmic reticulum, and obtained by homogenization and differential centrifugation of muscle tissue. CA2+ -ATPase expressed in transfected cell cultures will be also used. The chemical derivatization experiments will be complemented by expression of mutated cDNA in cell cultures. Microsomes prepared from transfected cells display a very active transport activity, and constitute a highly favorable system for studies of specific mutations. The collaborators have a long standing record of productive collaboration. The biological significance of this research is related to control of contractile activation and relaxation in muscle fibers. Its chemical significance is related to enzyme kinetics and catalysis, coupling of catalytic and transport activities, channels and transmembrane fluxes of electrolytes, and structure of proteins.
