TRINITROPHENYL-ATP AND TRINITROPHENYL-ADP BIND TO A SINGLE NUCLEOTIDE SITE ON ISOLATED BETA-SUBUNIT OF ESCHERICHIA-COLI F1-ATPASE - INVITRO ASSEMBLY OF F-1-SUBUNITS REQUIRES OCCUPANCY OF THE NUCLEOTIDE-BINDING SITE ON BETA-SUBUNIT BY NUCLEOSIDE TRIPHOSPHATE