Avtor/Urednik		Zorko, Matjaž; Pooga, Margus; Saar, Kuelliki; Razaei, Khadijeh; Langel, Uelo
Naslov		Differential regulation of GTPase activity by mastoparan and galparan
Tip		članek
Vir		Arch Biochem Biophys
Vol. in št.		Letnik 349, št. 2
Leto izdaje		1998
Obseg		str. 321-8
Jezik		eng
Abstrakt		The chimeric peptide galparan, composed of galain(1-13) in the N-terminus and mastoparan in the C-terminus, was recently designed and synthesized. The effect of galparan on GTPase activity of rat brain cortical membranes was studied in comparison with the effect of mastoparan and galanin. GTPase was activated by mastoparan but it was noncompetitively inhibited by galparan, while no effect of galanin and galanin(1-13) was found in this tissue. EC50 of 12.1 +- 2.1 micro M and Hill coefficient of 2.1 +- 0.6 was calculated for galparan from a dose-response curve and K1 of 19.1 +- micro M was obtained by fitting the experimental data to the Michaelis-Menten equation valid in the presence of noncompetitive inhibitor. mastoparan reversed the effect of galparan in a fully competitive manner while benzalkonium chloride did not prevent the inhibition of GTPase activity by galparan. pertussis-catalyzed ribosylation of G proteins from rat brain cortical membranes resulted in 15% lower basal GTPase activity of our preparation but did not alter the parameters of the dose-response curve for galparan inhibition. The rate of GTP gama S binding to G proteins from rat brain cortical membranes was not influenced by galparan. CD spectra revealed predominantly antiparallel beta-structure and unordered secondary structure of galparan in the buffer solution, while in the presence of lipid vesicles it adopted a higher amount of alpha-helix. Critical micelle concentration of galparan in buffer solution of 22 gama M was determined. it is suggested that the reversal of GTPase activation by mastoparan to inhibition by galparan is due to different loci of action of these two peptides on G proteins.
Deskriptorji		GTP PHOSPHOHYDROLASE WASP VENOMS CEREBRAL CORTEX CHIMERIC PROTEINS G-PROTEINS RATS, WISTAR CELL MEMBRANE GUANOSINE TETRAPHOSPHATE GUANOSINE 5'-O-(3-THIOTRIPHOSPHATE) PERTUSSIS TOXINS KINETICS PROTEIN BINDING