Isolation and characterization of a mutant of Neurospora crassa deficient in general amino acid permease activity

Identification of the Gene at the pmg Locus, Encoding System II, the General Amino Acid Transporter in Neurospora crassa

“…Mutations at the pmg locus disrupt the function of the general amino acid transport system, called system II, in N. crassa (DeBusk and DeBusk, 1980;Rao et al, 1975). The gene at the pmg locus has a high degree of sequence similarity (41% identity) to the general amino acid permease of Sa.…”

“…This region of the chromosome also contains the pmg gene, which has been reported to lie within 1 map unit of the pyr-4 locus (Perkins et al, 2000). As described in the Introduction, a mutation at the pmg locus had been shown many years ago to eliminate the general amino acid transport system in N. crassa (Rao et al, 1975).…”

“…The distinguishing phenotype of the pmg Ϫ mutant strain is that it confers resistance to FPA in a genetic background that is also pmb Ϫ mtr Ϫ . The medium used in this growth test contained NO 3 Ϫ as the sole nitrogen source because expression of the general amino acid transport system is repressed by high levels of NH 4 ϩ (Rao et al, 1975). We compared the growth of gap RIP , wild-type, pmg Ϫ , pmb Ϫ mtr Ϫ , and pmb Ϫ mtr Ϫ pmg Ϫ strains (Table 1).…”

“…Resistance to lcanavanine was used to identify the pmb locus (Pall, 1970;Thwaites and Pendyala, 1969). The pmg Ϫ strain, which lacks system II, was obtained by selecting for resistance to p-flurophenylalanine (FPA) in the pmb Ϫ , mtr Ϫ doublemutant strain (Rao et al, 1975).…”

Sequence and structure of mtr, an amino acid transport gene of Neurospora crassa

“…The constitutive transport systems were additionally defined by genetic analyses, which demonstrated independent segregation of genes controlling these transport systems (Rao et al 1975). The loci controlling the N, B, and G transport systems are called mtr, pmb, and pmg, respectively (Perkins et al 1982;Stuart et al 1988).…”