Gene: pyrimidine-3 IVR
pyrimidine-3
locus: pyr-3
locus_name: pyrimidine-3
organism_type: B
chromosome_number: IV
chromosome_side: R
link_group: IVR
cultural_requirements: IVR. Right of the T(NM152) left breakpoint and of T(S1229); hence, right of arg-14. Left of his-5 (1%) (238, 808). (482) Requires uracil or other pyrimidine (683). Growth inhibited by purine nucleosides and nucleotides (825). Structural gene for pyrimidine-specific carbamyl phosphate synthase (CPS) and aspartate carbamyl transferase (ACT; also abbreviated ATC) (456, 850) (Fig. 20). Mutants may lack either or both activities, e.g., those carrying alleles KS43 (CPS+ ACT-), KS20 (CPS- ACT+), and KS11 (CPS- ACT-) (1140). Unlike Saccharomyces, no feedback-insensitive CPS+ ACT+ mutants of Neurosporahave been discovered (A. Radford, unpublished data). Some mutants have kinetically altered aspartate carbamyl transferase (456, 880). Used extensively for studies of channeling and relation of gene structure to the two enzyme activities (236). Normally, carbamyl phosphate produced by pyr-3+ is used solely for pyrimidine synthesis, and carbamyl phosphate produced by arg-2+ and arg-3+ is used for arginine synthesis, the enzymes being in different organelles; however, a deficiency of the next enzyme in either pathway permits overflow of carbamyl phosphate into the other pathway (reviewed in reference 236). Hence, CPS- ACT+ alleles are suppressed by arg-12s (246), and CPS+' ACT- alleles can be selected as suppressors of arg-2and arg-3 (658, 887, and references therein). Some of the CPS+ ACT- mutations, called pyr-su-arg, suppress the arginine requirement but retain enough aspartate carbamyl transferase activity that they have no detectable pyrimidine requirement (877, 881). arg-13, arg-4, arg-5, arg-6, and am partly suppress CPS- ATC+ alleles (see reference 660). Fine-structure map (851, 1050). Fertility of interallelic crosses is variable and often very poor (658). Complementation between CPS- ACT+ and CPS+ ACT- mutants (246) and between some pairs of CPS+ ACT- mutants is good; otherwise, complementation is poor (849, 1159). Complementation maps (658, 849, 877, 1159). Mutational analysis (852). Direction of translation, based on enzyme types of polar mutants, is from CPS to ACT (850). Allele 37815(t) is heat sensitive (34°C versus 25 C) (68). Allele 1298 is C02 remediable (191, 192). Strain KS12, a pyr-1 pyr-3 double mutant, was originally called pyr-5 (see reference 346). The different classes of pyr-3 alleles have been called M (CPS-P-less), N (ACT-less), and MN (lacks both activities).
enzyme_id: 75
Enzyme: aspartate transcarbamylase carbamyl phosphate synthase
anid_name: pyrABCN
near_l: T(NM152) left breakpoint and T(S1229);arg-14
near_r: his-5
neu_name:
supplement: uracil or pyrimidine
image_url:
Strains
References
