THE 2 ALLELES OF THE HAPP GENE IN PHYSARUM-POLYCEPHALUM CODE FOR DIFFERENT PROTEINS

Many mRNAs show cell-type specific expression in the acellular slime m old Physarum polycephalum. The most abundant plasmodial-specific mRNA (hapP) encodes a small hydrophobic protein of 187 amino acids that con tains a potential signal peptide. Southern hybridizations using the ha pP cDNA showed that the hapP gene is a single copy gene with two allel es, hapP1 and hapP2. The alleles have restriction enzyme polymorphisms . The nucleotide sequence of the coding region of the hapP1 allele was obtained from a genomic clone, and the nucleotide sequence of the hap P2 allele was obtained from a cDNA clone. The hapP1 and hapP2 alleles code for proteins that are 9.6% different in amino acid sequence. All differences are found in the central region of the protein. The nucleo tide sequences of the first and last exons, which contain coding and n on-coding regions, are identical. PCR amplification of cDNAs (RT-PCR) showed that both alleles are expressed in the same cell.