Allosteric behavior in the activation of transducin mediated by rhodopsin

Conference · Thu May 01 04:00:00 EDT 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5326846

Wessling-Resnick, M; Johnson, G I

Transducin is a member of the family of regulatory GTP-binding proteins which provide a signal transduction mechanism for many cell surface receptors. These receptors act in a catalytic manner to displace GDP bound to the G protein in exchange for GTP during a process referred to as activation. The authors have studied the steady-state kinetics of the activation of transducin mediated by rhodopsin by employing the non-hydrolyzable GTP analog, (/sup 35/S)-GTP..gamma..S. The substrate-velocity curves display remarkable allosteric behavior with a Hill coefficient, n/sub H/ = 2. Lineweaver-Burke plots with respect to reciprocal (transducin) show curvilinearity indicative of positive cooperativity. However, a series of parallel lines are generated by plotting the linear transformation as (transducin)/sup -2/. The double reciprocal plots with respect to (GTP..gamma..S) are a series of parallel lines. The initial rate analysis supports a double displacement catalytic mechanism for the molecular interactions between the photon receptor, G protein, and guanine nucleotides. It remains to be determined whether the positive cooperative behavior the authors observe can be assigned to the interaction of multiple transducins with rhodopsin, the presence of an allosteric effector, or hysteresis in the receptor's activity. These unique observations also provide insight into the molecular interactions of members of the family of G protein-coupled receptors.

• Research Organization: Univ. of Massachusetts Medical Center, Worcester
• OSTI ID: 5326846
• Report Number(s): CONF-8606151-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:6
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
DAYS LIVING RADIOISOTOPES
ELEMENTARY PARTICLES
EVEN-ODD NUCLEI
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MASSLESS PARTICLES
MEMBRANE PROTEINS
MOLECULAR BIOLOGY
NUCLEI
ORGANIC COMPOUNDS
PHOTONS
PIGMENTS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
RECEPTORS
RHODOPSIN
SULFUR 35
SULFUR ISOTOPES
TRACER TECHNIQUES