While G protein activated inwardly rectifying K"+ channels (GIRKs) are activated by binding of the #beta##gamma# subunits of an activated G protein, the molecular mechanism of gating of GIRKs by G_#beta#_#gamma# remains obscure. In order to elucidate the possible role of putative cytoplasmic regions of the GIRK1/GIRK5 channel in G protein- dependent and intrinsic gating of the channel, synthetic peptides derived from the GIRK1 sequence were designed.

The O intermediate of the photocycle of bacteriorhodopsin (BR) was studied by absorption kinetic measurements at different actinic light densities, With increasing exciting flash intensity, the relative yield of O slightly increases,,while that of M(f) strongly decreases at the expense of M(s). Kinetic calculations and the optical anisotropy of O show that O can be formed only from M(f) although M(f) and O have different light intensity dependences,

In order to further investigate a G-protein activated inwardly rectifying potassium channel subunit, GIRK1 was expressed in Xenopus oocytes (where it coassembles with the endogenous GIRK5). The mechanism underlying ion permeation and rectification were measured in isolated inside-nut patches. Single channel current amplitudes under symmetrical K+ concentrations at different holding potentials were evaluated. Inward-rectification of K+-currents through

1. In order to find out the functional roles of cytosolic regions of a G protein-activated, inwardly rectifying potassium channel subunit we studied block of GIRK channels, expressed in Xenopus laevis oocytes, by synthetic peptides in isolated inside-out membrane patches. 2. A peptide (DS6) derived from the very end of the C-terminus of GIRK1 reversibly blocked GIRK activity with IC50 values of 7.9 +/- 2.0 or 3.5 +/- 0.5 mu g ml(-1) (corresponding

omega -Conotoxins selective for N-type calcium channels are useful in the management of severe pain. In an attempt to expand the therapeutic potential of this class, four new omega -conotoxins (CVIA-D) have been discovered in the venom of the piscivorous cone snail, Conus catus, using assay-guided fractionation and gene cloning. Compared with other omega -conotoxins, CVID has a novel loop 4 sequence and the highest selectivity for N-type over P/Q-type

In the present study, two-electrode voltage-clamp techniques have been used to assess the interaction between the MVIIA omega -conotoxin and an isoform of the N-type Ca2+ channel alpha subunit (alpha (1B-d)). Cloned alpha (1B-d) Ca2+ channels were expressed in Xenopus laevis oocytes in the presence and absence of the beta (3) subunit. Coexpression of the beta (3) subunit significantly shifted the IC50 value for MVIIA inhibition of central N-type