Coupling of photoexcited rhodopsin to inositol phospholipid hydrolysis in fly photoreceptors.

Fly photoreceptor membranes were used to test the effect on defined biochemical reactions of light and of compounds causing photoreceptor excitation. Complementary electrophysiological studies examined whether putative second messengers excite the fly photoreceptor cells. This analysis revealed the following sequence of events: photoexcited rhodopsin activates a G protein by facilitating GTP binding.

Light-activated guanosinetriphosphatase in Musca eye membranes resembles the prolonged depolarizing afterpotential in photoreceptor cells.

Measurement of light-dependent GTPase (EC 3.1.5.

The kinetic dissection of transport from metabolic trapping during substrate uptake by intact cells. Uridine uptake by quiescent and serum-activated Nil 8 hamster cells and their murine sarcoma virus-transformed counterparts.

1. We present a theoretical analysis of the tandem processes of transport and metabolic trapping which together constitute uptake of a substrate by intact cells. 2.

Nucleoside transport in mammalian cell membranes. III. Kinetic and chemical modification studies of cytosine-arabinoside and uridine transport in hamster cells in culture.

Transport of the nucleoside analog cytosine-arabinoside (CAR) in transformed hamster cells in culture has been studied in conditions of minimal metabolic conversion. Uptake (zero-trans in) properties at 20 degrees C over a limited range of CAR concentrations were characterized by a Km of 350 micrometer and a maximal velocity (V) of 780 micrometer.min-1 (V/Km = 2.