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Recombinant protein segments from a metabotropic glutamate receptor and from an odorant receptor were used as substrates in protein kinase C phosphorylation assays. Protein kinase Cβ and δ phosphorylated an intracellular consensus phosphorylation site in the metabotropic glutamate receptor Only protein kinase Cδ phosphorylated a novel extracellular consensus phosphorylation site in the odorant receptor. These results suggest differential regulation of these receptors by protein kinase C isotypes.

Recombinant protein segments from a metabotropic glutamate receptor and from an odorant receptor were used as substrates in protein kinase C phosphorylation assays. Protein kinase Cbeta and delta phosphorylated an intracellular consensus phosphorylation site in the metabotropic glutamate receptor. Only protein kinase Cdelta phosphorylated a novel extracellular consensus phosphorylation site in the odorant receptor. These results suggest differential regulation of these receptors by protein kinase C isotypes.

Individual anomeric protons that are unresolved in the one-dimensional 250-MHz spectra of oligomannosidic glycopeptides can be separated and characterized by two-dimensional J-resolved NMR spectroscopy. Homogeneous preparations of ovalbumin glycopeptides Man6GlcNAc2Asn and Man5GlcNAc2Asn were characterized by chemical methods, conventional proton NMR, and two-dimensional J-resolved NMR. Due to characteristic differences in coupling constants, mannose (J1,2 less than or equal to 2 Hz) and N-acetylglucosamine (J1,2 approximately 9 Hz) anomeric signals of similar chemical shift were readily separated and identified in the two-dimensional spectra. It is shown that two-dimensional J-resolved NMR spectroscopy, in combination with conventional NMR and limited chemical analysis, is a rapid and reliable technique for the determination of glycopeptide primary structure.

The expression of genes encoding G-protein beta gamma subunits was investigated in isolated olfactory receptor neurons from channel catfish. DNA sequencing of PCR products showed that the beta 1, beta 2, gamma 2 and gamma 3 genes were expressed in the neurons. Western blotting showed that at least three of these subunit proteins were expressed. This first analysis of the expression of beta gamma genes in olfactory receptor neurons suggests that these subunits may be involved in a variety of transduction events in these cells.

The luteinizing hormone/human choriogonadotropin (hCG) receptor from superovulated rat ovary was purified to homogeneity. A novel scheme based on reverse immunoaffinity chromatography using immobilized antibodies to membrane proteins from receptor down-regulated ovary and subsequent two-step affinity purification on hCG-Sepharose was used to isolate homogeneous receptor. The purification method was also compared to an alternate scheme involving lectin affinity chromatography followed by hCG affinity chromatography. The purified receptor obtained by the latter method was heterogeneous and highly aggregated. The hormone binding properties, molecular size, and subunit composition of the purified receptor obtained by either method were identical. The stability of the receptor during and following solubilization was markedly improved by using 20% glycerol. The pure receptor consists of four nonidentical subunits of molecular weight 79,300 (alpha), 66,400 (beta), 55,300 (gamma), and 46,700 (delta) as indicated by polyacrylamide gel electrophoresis under reducing conditions. All receptor subunits generally, but occasionally excepting the alpha-subunit, were specifically labeled with iodinated hCG in membrane and soluble receptor preparations using bifunctional cross-linking agents. Analysis of the cross-linked hormone-receptor complexes under nonreducing conditions showed the molecular mass of the undissociated receptor to be 268,000 daltons. Hormone binding studies demonstrated that the isolated receptor retained all of the specific binding characteristics expected for the luteinizing hormone/hCG receptor. In combination, these results indicate that the functional and structural properties of the receptor were not altered during purification.