FGSC #6136

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Reporting Genes: trp-3;su(trp-3td2)-2

Species: crassa

Allele: S1952(td2);su2

Alternate Strain Number: S1952-23-(11-4)A

Mutagen: MDAB

Depositor: ELT

Linkage Group: IIR;III

Mating Type: a

Species Number: 10

Deposit Sheet ↗

Genes

Locus	Cultural Requirements	Link Group	Type
su(trp-3td2)-2	III. Linked to leu-1 (22%) (581). Allele specific. Suppresses allele td2 but does not suppress td6, td7l, or any other allele from td1 through td34 (580, 1169). This and the other listed suppressors of td2 were not tested on later trp-3 alleles that fall in the same complementation group as td2. Although suppressed mutants grow on minimal medium, growth is stimulated by addition of tryptophan. Suppressed trp-3;sucolonies are morphologically distinguishable from those of the wild type. Tryptophan synthetase is formed at levels below that of the wild type. Originated in trp-3 allele td2 (originally numbered S1952) (1166, 1169). Called su-2 (388) and su2 (1169).	III	B
trp-3	IIR. Right of fl (2 to 6%). Left of rip-1 (9%) and un-5(10%) (816, PB). (1166). Uses tryptophan (685); strains carrying some alleles also use indole (4). Structural gene for tryptophan synthetase (1167), called tryptophan desmolase in early literature. Tryptophan synthetase catalyzes three reactions: indoleglycerol-phosphate -> tryptophan, indole tryptophan, and indoleglycerol-phosphate <-> indole (Fig. 11). In Neurospora, all three reactions are catalyzed by a single protein, which is specified by a single gene (645, 1167). Mutants lack indoleglycerol-phosphate -> tryptophan activity but differ with respect to the other activities; e.g., strains carrying trp-3 allele (td141 are blocked in indoleglycerol-phosphate utilization but can use indole; trp-3 (td100) can synthesize indole but not convert it to tryptophan; trp-3 (td140) lacks all three activities. (See references 582 and 1049 for citations and characteristics of other mutants.) Used extensively for studies of gene structure in relation to enzymatic activity (257, 582 and references therein, 1167). The active enzyme is a homooligomer (645) thought to have two domains (644 and references therein). Biochemical studies of complementation between alleles: in vivo (582, 583) and in vitro (1048 and references therein). Complementation maps (4, 5, 9 and references therein, 582). Fine-structure maps (5, 540, 582, 1049). Reviewed as example of gene fusion (218). trp-3 mutant C83 provided the first proved example in Neurospora of gene-controlled loss of enzyme activity (685); trp-3 mutant S1952 provided the first example of allele-specific suppression restoring functional wild-type-like enzyme (1166). Allele td140 is supersuppressible (954, 955). Certain classes of trp-3mutants are osmotic remediable (583). Called td and tryp-3.	IIR	B