Function of hisF and hisH gene products in histidine biosynthesis.

ABSTRACT The his1 gene (chromosome V) of Saccharomyces cerevisiae specifies phosphoribosyl transferase (E.C.2.4.2.17), the first enzyme of histidine biosynthesis. This hexameric enzyme has both catalytic and regulatory functions.—The spontaneous reversion rates of seven his1 mutations were studied. The reversion rates of the alleles at the proximal end of the locus (relative to the centromere) were about 50-fold higher than distal alleles.—Spontaneous reversion to prototrophy was studied in diploids homoallelic for each of the seven his1 mutations. Based on tetrad analysis, the prototrophy revertants could be assigned to three classes: (1) revertant tetrads that carried a prototrophic allele indistinguishable from wild type; (2) revertant tetrads that carried a prototrophic allele characterized by histidine excretion and feedback resistance; and (3) revertant tetrads that did not contain a prototrophic spore, but rather a newly derived allele that complemented the original allele intragenically. Four of the seven his1 mutations produced the excretor revertant class, and two mutations produced the complementer revertant class. The significance of these findings to our understanding of gene organization and the catalytic and regulatory functions of gene products are discussed.

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Identification of a baculovirus polyhedron formation mutant with a novel phenotype

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100166440 ◽

1996 ◽

Vol 54 ◽

pp. 796-797

Author(s):

James M. Slavicek ◽

Melissa J. Mercer ◽

Mary Ellen Kelly

Keyword(s):

Viral Gene ◽

Gene Products ◽

Type Number ◽

Infection Cycle ◽

Wild Type ◽

Protein Matrix ◽

Insect Midgut ◽

Viral Particles ◽

Budded Virus ◽

Viral Form

Nucleopolyhedroviruses (NPV, family Baculoviridae) produce two morphological forms, a budded virus form and a viral form that is occluded into a paracrystalline protein matrix. This structure is termed a polyhedron and is composed primarily of the protein polyhedrin. Insects are infected by NPVs after ingestion of the polyhedron and release of the occluded virions through dissolution of the polyhedron in the alkaline environment of the insect midgut. Early after infection the budded virus form is produced. It buds through the plasma membrane and then infects other cells. Later in the infection cycle the occluded form of the virus is generated (reviewed by Blissard and Rohrmann, 1990).The processes of polyhedron formation and virion occlusion are likely to involve a number of viral gene products. However, only two genes, the polyhedrin gene and 25K FP gene, have been identified to date that are necessary for the wild type number of polyhedra to be formed and viral particles occluded.

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New insights into heparan sulphate biosynthesis from the study of mutant mice

Biochemical Society Symposium ◽

10.1042/bss0690047 ◽

2002 ◽

Vol 69 ◽

pp. 47-57 ◽

Cited By ~ 8

Author(s):

Catherine L. R. Merry ◽

John T. Gallagher

Keyword(s):

Growth Factors ◽

Biosynthetic Pathway ◽

Heparan Sulphate ◽

Mutant Mice ◽

Gene Products ◽

Multiple Gene ◽

Adhesion Proteins ◽

Ligand Interactions

Heparan sulphate (HS) is an essential co-receptor for a number of growth factors, morphogens and adhesion proteins. The biosynthetic modifications involved in the generation of a mature HS chain may determine the strength and outcome of HS–ligand interactions. These modifications are catalysed by a complex family of enzymes, some of which occur as multiple gene products. Various mutant mice have now been generated, which lack the function of isolated components of the HS biosynthetic pathway. In this discussion, we outline the key findings of these studies, and use them to put into context our own work concerning the structure of the HS generated by the Hs2st-/- mice.

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