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Molecular and General Genetics MGG

, Volume 161, Issue 3, pp 297–304 | Cite as

A possible model for the structure of the Neurospora carbamoyl phosphate synthase-aspartate carbamoyl transferase complex enzyme

  • A. J. Makoff
  • F. P. Buxton
  • A. Radford
Article

Summary

The pyrimidine-3 locus of Neurospora crassa specifies a multienzyme complex comprising pyrimidine-specific carbamoyl phosphate synthase (CPSpyr) and aspartate carbamoyl transferase (ACT). It appears to be divided into a translationally proximal CPS-specific region and a distal ACT-specific region.

Levels of complementation for ACT activity between pairs of four pyr-3 CPS+ACT- mutants showed a range from 12% to 68% of the wild-type level of the enzyme. This is interpreted as interallelic complementation, contradicting certain earlier suggestions of two dissimilar ACT subunits.

Proteolysis of an extract from a heterokaryon formed from two of the above CPS+ACT- alleles (α and β) did not lead to loss of ACT activity, but led to the formation of a fragment with ACT activity with a similar molecular weight (92,000 daltons) to that produced in extracts of wild type strain.

The pyr-3 polar mutant 43–174, which is enzymatically CPS+ACT- and which fails to complement with any other CPS+ACT- alleles, thus suggesting its location towards the proximal end of the ACT region, has CPS activity associated with a form of 180,000 daltons molecular weight. These findings are used to construct a model for the structure of the native enzyme complex.

Keywords

Enzyme Wild Type Strain Native Enzyme Neurospora Crassa Carbamoyl 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag 1978

Authors and Affiliations

  • A. J. Makoff
    • 1
  • F. P. Buxton
    • 1
  • A. Radford
    • 1
  1. 1.Department of GeneticsThe University of LeedsLeedsU.K.

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