The GTP-binding protein G alpha s is present in dormant spores and expressed differentially during spore germination of the fungus Phycomyces blakesleeanus.
A DNA sequence homologous to a G alpha s DNA probe, and the corresponding G alpha s protein (stimulatory alpha-subunit of GTP-binding protein) were detected in Phycomyces blakesleeanus. The protein was demonstrated in membrane fractions of dormant spores of this fungus using three different experimental approaches. Photoaffinity-labelling experiments with [alpha-32P]GTP of the membrane fraction revealed two bands, of 56 and 32 kDa. The 56 kDa GTP-binding protein was detected by this method in all the stages of early development and growth investigated. Also, a spore protein of 56 kDa was ADP-ribosylated by cholera toxin, and a 56 kDa protein was detected by Western blotting with a specific antibody against mammalian G alpha s. These results indicate that G alpha s (56 kDa) is present in dormant spores of P. blakesleeanus. Using the ADP-ribosylation and Western blotting assays, G alpha s was detected during all stages of spore germination before the hyphae became highly branched, but it was not detected in the branched hyphae that formed 18 h after the initiation of spore germination. Therefore, G alpha s is expressed differentially during Phycomyces development.
Martínez-Cadena
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G
Instituto de Investigación en Biología Experimental, Facultad de Química, Universidad de Guanajuato, Mexico.
Novoa-Martínez
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G
González-Hernández
A
A
García-Soto
J
J
D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000345:Affinity Labels; D002772:Cholera Toxin / Q000494:pharmacology; D004271:DNA, Fungal / Q000235:genetics; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D006160:Guanosine Triphosphate; D010800:Phycomyces / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D013172:Spores, Fungal / Q000235:genetics / Q000502:physiology
D000345:Affinity Labels; D004271:DNA, Fungal; D000246:Adenosine Diphosphate Ribose; D006160:Guanosine Triphosphate; D002772:Cholera Toxin; D019204:GTP-Binding Proteins