CHARACTERIZATION OF THE GLYCERALDEHYDE-3-PHOSPHATE DEHYDROGENASE GENEFAMILY FROM KLUYVEROMYCES-MARXIANUS - POLYMERASE CHAIN REACTION-SINGLE-STRAND CONFORMATION POLYMORPHISM AS A TOOL FOR THE STUDY OF MULTIGENIC FAMILIES

Three glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes from Kluy veromyces marxianus were identified and characterized. The coding regi on of two of them (GAP2 and GAP3) is very similar (99.6% homology). Th e other gene (GAP1) is only 86% homologous to GAP2 or GAP3 and is resp onsible for the expression of Gap1p. This protein is extremely homolog ous to the K. marxianus cell wall protein p37, presumably involved in flocculation. However, no leader sequence could be detected in this ge ne. The identification of the three genes was possible with the use of polymerase chain reaction-single-strand conformation polymorphism (PC R-SSCP), as it permits us to overcome the difficulties caused by the h igh homology amongst the genes. Expression of the GAPDH genes under di fferent carbon sources (glucose or ethanol) was assessed either by Nor thern blot or reverse transcription-PCR SSCP analysis, revealing that genes GAP1 and GAP2, but not GAP3, are transcribed. The results also i ndicate that the transcription of the gene encoding the cell wall prot ein p37 (Gap1p) is not dependent on the carbon source, in contrast wit h the expression of the gene GAP2, which is affected in cells growing in a glucose-depleted medium.