Substitution of three amino acid switches receptor specificity of Gqalpha to that of Gialpha

Article Abstract:

The hypothesis that the ability of G proteins to differentiate among specific receptor subsets is determined by certain amino-acid residues located at the alpha-subunit C-termini is tested. Alphaq/alpha12 chimaeras mediating phospholipase C stimulation by receptors otherwise coupled to Gi were produced by substituting alphai2 residues for alphaq C-terminal acids. Results revealed that three alphai2 amino acids are were enought to cause a switch in the chimaeras' receptor specificity. This suggests that a C-terminal turn centered on a glycine three-residues away from the C-terminus has a significant role in the specification of receptor interactions of G proteins belonging to the Gi/Go/Gz family.

Lectins, Amino acid sequence, Amino acid sequencing, Lectin structure-activity relationships

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The arginine finger strikes again

Article Abstract:

Research which has identified the three-dimensional structures of Ras and two other GTPases has made it possible to establish how these proteins are turned off when the GTP is hydrolyzed to GDP by GTPase-activating proteins (GAPs). It has been found that there are three structurally independent protein machines that use identical mechanisms to promote GTP hydrolysis. There could be several uses for the ability of RGS and GAP proteins to distinguish between the ground and transition states.

Protein binding, Ras genes

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Mouse coat colour reconsidered

Article Abstract:

Hyperactivation of the agouti protein in mice with a dominant yellow mutuation results in yellow coat color, obesity, diabetes and tumor. Injection of melanocyte-stimulating hormone receptor (MSH-R) overrides the effect of mutation on coat colour, but it does not counteract the other effects. The protein products of adenylycydase and G alpha s genes are necessary for MSH-driven coat-darkening, though the genes are not defined by coat-color loci.

Genetic aspects, Mice, Mice (Rodents), Letter to the Editor, Color of animals, Animal coloration, Animal mutation

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