Intragenic suppressors that restore the activity of the maturase encoded by the second intron of the Saccharomyces cerevisiae cyt b gene.

The protein encoded by the second intron (bi2) of the mitochondrial cyt b gene from Saccharomyces cerevisiae functions as a maturase promoting intron splicing. This protein belongs to a large family characterized by the presence of two conserved motifsauthor="alan" time="20040513T082332+0000":author="alan" time="20040513T082334+0000" data=";" LAGLIDADG (or P1 and P2). We have isolated and characterized spontaneous revertants from two mis-sense mutations, G85D and H92Pauthor="alan" time="20040513T082434+0000" data=","author="alan" time="20040513T082437+0000" (localized in the P1 motif of the bi2author="alan" time="20040513T083211+0000"-author="alan" time="20040513T082359+0000" data="-"maturaseauthor="alan" time="20040513T082439+0000"), that have a detrimental effect on intron splicing. All analyzed revertants are intragenic and resulted from monosubstitutions in the mutated codons. Only true backauthor="alan" time="20040513T082508+0000"-author="alan" time="20040513T082508+0000" data=" "mutations author="alan" time="20040513T082526+0000"that restorauthor="alan" time="20040513T082528+0000"eauthor="alan" time="20040513T082529+0000" data="ing" the initial glycineauthor="alan" time="20040513T082515+0000" author="alan" time="20040513T082512+0000" data=" "85 and a pseudoreversion that replaces the deleterious aspartic acidauthor="alan" time="20040513T082531+0000" author="alan" time="20040513T082530+0000" data=" "85 by alanine were found in revertants of the mutant G85D. In contrast, all possible monosubstitutions in the mutated codon H92P were identified among the revertants of this mutant. The maturase activity of all novel forms of the protein is similar to the wild-type protein. [ABSTRACT FROM AUTHOR]