Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0043167 (pertussis)
 19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transducin, a GTP-binding protein involved in phototransduction in the vertebrate retina, belongs to a family of homologous coupling proteins that also includes Gs and Gi, the regulatory proteins of adenylate cyclase. Here we report the cDNA sequence and deduced amino acid sequence of transducin's alpha subunit (T alpha). The cDNA was isolated, by screening with an antibody probe, from a bovine retinal cDNA library in the expression vector lambda gt11. The 2.2-kilobase cDNA insert hybridized to a single 2.6-kilobase poly(A)+ RNA species present in extracts of bovine retina but not of bovine heart, liver, or brain. The nucleotide sequence of the cDNA revealed an open reading frame long enough to encode the entire 39-kDa T alpha polypeptide. The polypeptide sequence deduced from the cDNA would be composed of 350 amino acids and have a molecular weight of 39,971. Portions of the sequence matched reported amino acid sequences of T alpha tryptic fragments, including sites specifically ADP-ribosylated by cholera and pertussis toxins. The predicted sequence also includes four segments, ranging from 11 to 19 residues in length, that exhibit significant homology to sequences of GTP-binding proteins, including the ras proteins of man and yeast and the elongation factors of ribosomal protein synthesis in bacteria, EF-G and EF-Tu. In combination with previous functional studies of tryptic fragments of T alpha, the deduced amino acid sequence makes it possible to predict which portions of the polypeptide interact with other molecules involved in retinal phototransduction.
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PMID:Amino acid sequence of the alpha subunit of transducin deduced from the cDNA sequence. 240 55

Previously it has been shown that persistent activation of the stimulatory adenylyl cyclase pathway with cholera toxin (CT) downregulates the Gs alpha polypeptide (80%) in a cAMP-independent manner in C6 glioma cells (Shah, 1997). This study was conducted to examine the short and long term effects of CT on the regulation of pertussis toxin-sensitive and -insensitive G proteins and their transcripts in C6 glioma cells. Treatment of C6 cells with CT (100 ng/ml) up to 16 h had no effect on either Gi or Gq/11 alpha proteins. However, prolonged exposure (24-48 h) caused increased expression of Gi (20-30%) and Gq/11 alpha proteins (40%). Urea gradient gels, which can separate Gq alpha and G11 alpha proteins, revealed that prolonged CT treatment increased the expression of both of these G proteins. The CT-mediated enhanced expression of Gq alpha and G11 alpha proteins was accompanied by increased mRNA levels of these proteins as determined by RT/PCR. Cyclic-AMP elevating agents like forskolin (10 microM) and db-cAMP (1 mM) mimicked the effect of CT on Gi but not Gq/11 alpha proteins. These studies show long term cAMP-dependent regulation of Gi and cAMP-independent expression of Gq/11 alpha proteins in C6 glioma cells.
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PMID:Cholera toxin mediated regulation of the expression of Gq alpha and G11 alpha GTP binding proteins. 1041 Mar 8