Robert P. Lawther

Analysis of the functional domains of biosynthetic threonine deaminase by comparison of the amino acid sequences of three wild-type alleles to the amino acid sequence of biodegradative threonine deaminase.

The nucleotide sequence of the gene, ilvA, for biosynthetic threonine deaminase (Tda) from Salmonella typhimurium was determined. The deduced amino acid sequence was compared with the deduced amino acid sequences of the biosynthetic Tda from Escherichia coli K-12 (ilvA) and Saccharomyces cerevisiae (ILV1) and the biodegradative Tda from E. coli K-12 (tdc). The comparison indicated the presence of two types of blocks of homologous amino acids. The first type of homology is in the N-terminal portion of all four isozymes of Tda and probably indicates amino acids involved in catalysis. The second type of homology is found in the C-terminal portion of the three biosynthetic isozymes and presumably is involved in either (i) the binding or interaction of the allosteric effector isoleucine with the enzyme, or (ii) subunit interactions. The sites of amino acid changes of two E. coli K-12 ilvA alleles with altered response to isoleucine are consistent with the conclusion that the C-terminal portion of biosynthetic Tda is involved in allosteric regulation.

Isolation of recombinant bacteriophage containing male-specific mouse DNA

SummaryThe mammalian Y chromosome is an isolated piece of genetic material that directs sexual determination and gametogenesis. Very little is understood about the mechanism whereby the Y chromosome carries out these functions. Also, there is a severe lack of genetic markers on this chromosome. In order to understand the structure and function of the Y chromosome at the level of its DNA sequences and to provide genetic markers, we are isolating clones of DNA whose sequences are found primarily in DNA from male mice. To this end, we have developed a procedure for the identification of such clones. Application of this screening procedure to a lambda library derived from mouse sperm DNA has yielded 12 distinct clones, part of whose sequences are present predominantly in male DNA. Besides this DNA, they also contain other sequences that are shared with female DNA. These clones are either derived from the Y chromosome or they represent autosomal sequences specifically amplified during male development.

Tissue Expression Pattern of Class II and Class V Genes Found in the Adh Complex on Mouse Chromosome 3

The alcohol dehydrogenase enzymes in mice and humans are encoded by a linked group of genes in the same transcriptional orientation. The enzymes play important roles in alcohol metabolism and retinoid signaling and homeostasis. The expression patterns at the mRNA level of the mouse Adh4 (class II) gene and the recently identified Adh6a and Adh6b genes (class V) are now reported to complete this analysis for the entire family. Adh4 is expressed at high levels in liver and is detectable in small intestine and testes. Adh6b is expressed in liver but Adh6a is not. Adh6a is expressed at high levels in small intestine while Adh6b is not. Adh6a expression is detectable in the female adrenal and not at all in the male adrenal, but Adh6b is expressed at moderate levels in both sexes. Although Adh6a and Adh6b have expression patterns different from each other, neither expresses like any other gene in the complex, suggesting different control mechanisms and possibly different functions.