Molecular and General Genetics MGG

, Volume 103, Issue 2, pp 185–193 | Cite as

Organization of the Histidine-3 region of Neurospora

  • Asad Ahmed


The histidine-3 region of Neurospora specifies the structure of three enzymes of the histidine biosynthetic pathway viz., PR-AMP 1,6-cyclohydrolase, PR-ATP pyrophosphohydrolase, and histidinol dehydrogenase. Point mutations in this region may either affect individual enzyme activities or all of the three activities simultaneously. Attempts have been made to fractionate the three enzymes in order to understand the organization of the his-3 region. Gel-filtration on Sephadex G-200 revealed a single peak of activity for pyrophosphohydrolase and dehydrogenase. The two enzymes also emerged as one peak on chromatography through a DEAE-cellulose column eluted with linear salt gradient. Sedimentation characteristics of cyclohydrolase, pyrophosphohydrolase, and dehydrogenase were identical on sucrose density-gradient centrifugation. The molecular weight of this aggregate was estimated to be about 140,000. Other enzymes of histidine biosynthesis could be readily separated by these methods. Furthermore, mutational events occurring at several points across the genetic map seem to influence the three activities simultaneously. These results suggest that the polypeptides coded by the his-3 region are organized into a functional aggregate or multi-enzyme complex. Analysis of existing four-point cross data indicates that recombination within his-3 region is polarized. This polarity, according to the model proposed by Bernstein (1964), is towards the centromere and proceeds in a direction opposite to translation as deduced from complementation.


Enzyme Histidine Sedimentation Characteristic Individual Enzyme Salt Gradient 
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.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Ahmed, A.: A multi-enzyme complex specified by the histidine-3 region of Neurospora. (Abstract). Genetics 54, 316 (1966).Google Scholar
  2. —: The nature of complementation among mutants in the histidine-3 region of Neurospora crassa. Brookhaven Symp. Biol. 17, 53–65 (1964).Google Scholar
  3. Ames, B. N., R. F. Goldberger, P. E. Hartman, R. G. Martin, and J. R. Roth: The histidine operon. In: Regulation of nucleic acid and protein biosynthesis, p. 272–287 (ed. V. V. Koningsberger and L. Bosch). Amsterdam: Elsevier Publ. Co. 1967.Google Scholar
  4. —: Chromosomal alterations affecting the regulation of histidine biosynthetic enzymes in Salmonella. J. molec. Biol. 7, 23–42 (1963).Google Scholar
  5. Bernstein, H.: On the mechanism of intragenic recombination. II. Neurospora crassa. J. theoret. Biol. 6, 347–370 (1964).Google Scholar
  6. Creaser, E. H., D. J. Bennett, and R. B. Drysdale: The purification and properties of histidinol dehydrogenase from Neurospora crassa. Biochem. J. 103, 36–41 (1967).Google Scholar
  7. Giles, N. H., M. E. Case, C. W. H. Partridge, and S. I. Ahmed: A gene cluster in Neurospora crassa coding for an aggregate of five aromatic synthetic enzymes. Proc. nat. Acad. Sci. (Wash.) 58, 1453–1460 (1967).Google Scholar
  8. Imamoto, F., J. Ito, and C. Yanofsky: Polarity in the tryptophan operon of E. coli. Cold Spr. Harb. Symp. quant. Biol. 31, 235–249 (1966).Google Scholar
  9. Lowry, O., N. J. Rosebrough, A. L. Farr, and R. J. Randall: Protein measurement with the folin phenol reagent. J. biol. Chem. 193, 265–275 (1951).Google Scholar
  10. Martin, R. G., and B. N. Ames: A method for determining the sedimentation behavior of enzymes: Application to protein mixtures. J. biol. Chem. 236, 1372–1379 (1961).Google Scholar
  11. —: A molecular model of the phenomenon of polarity. Cold Spr. Harb. Symp. quant. Biol. 31, 215–220 (1966).Google Scholar
  12. Murray, N. E.: Polarized recombination and fine structure within the me-2 gene of Neurospora. Genetics 48, 1163–1183 (1963).Google Scholar
  13. —: Polarized intragenic recombination in chromosome rearrangements of Neurospora. Genetics 58, 181–191 (1968).Google Scholar
  14. Newton, A.: Effect of nonsense mutations on translation of the lactose operon of Escherichia coli. Cold Spr. Harb. Symp. quant. Biol. 31, 181–187 (1966).Google Scholar
  15. Stadler, D. R., and A. M. Towe: Recombination of allelic cysteine mutants in Neurospora. Genetics 48, 1323–1344 (1963).Google Scholar
  16. Webber, B. B.: Biochemical and genetical studies of histidine requiring strains of Neurospora crassa. Ph. D. thesis, Yale University (1959)Google Scholar
  17. —: Genetical and biochemical studies of histidine requiring mutants of Neurospora crassa. III. Correspondence between biochemical characteristics and complementation map position of hist-3 mutants. Genetics 51, 263–273 (1965a).Google Scholar
  18. —: IV. Linkage relationships of hist-3 mutants. Genetics 51, 275–283 (1965b).Google Scholar
  19. —: Genetical and biochemical studies of histidine requiring mutants of Neurospora crassa. I. Classification of mutants and characterization of mutant groups. Genetics 45, 1605–1615 (1960).Google Scholar

Copyright information

© Springer-Verlag 1968

Authors and Affiliations

  • Asad Ahmed
    • 1
  1. 1.Department of GeneticsUniversity of AlbertaEdmontonCanada

Personalised recommendations