PubMed Health⌕ Search

Biomedical subjects

F M Hoffmann

Publications and source records attributed to F M Hoffmann.

59 records · Page 4Linked to original sources
PubMed1976

Maintainance of specificity, information, and thermostability in thermophilic Bacillus sp. glutamine synthetase.

Glutamine synthetase has been purified to homogeneity from B. subtilis (37 degrees) B. stearothermophilus (55 degrees), and B. caldolyticus (75 degrees). Those characteristics compared include size (6.0 +/- 0.3 X 10(5) daltons), quaternary structure (12 SU) amino acid content, substrate Km's and specificity for structural analogs, metal ion activation, number and kind of separate feedback modifier sites, and the complexity of modifier-substrate and modifier-modifier site interactions. Although the 37 degrees and 55 degrees systems are quite similar, the 75 degrees system shows important alterations in substrate specificity and modes of modifier action. Whereas at 37 degrees and 55 degrees AMP inhibits synergistically with amino acids (glycine, glutamine, histidine), the 75 degrees enzyme is inhibited directly by the products ADP, (which assumes the role of AMP) and glutamine, plus other ligands. Ligand binding domains are compared and found to be very different. Thermostabilization occurs by (a) protection by bound L-glutamate, (b) protein aggregation, (c) trends in the content of total polar residues, total Asx + Flx residues, the average hydrophobicity, and (d) disulfide bond cross-linking. Such studies provide insights to molecular evolution occurring with changes in environmental stress.

Adenine Nucleotides↗
PubMedDate not supplied

Drosophila abl and genetic redundancy in signal transduction.

Genetic studies on Drosophila Abl and, more recently, on mouse c-Abl and c-Src indicate that the functions of these non-receptor tyrosine kinases may duplicate activities of other molecules within signal transduction pathways. In Drosophila, second-site mutations have been recovered that disrupt the redundant functions so that the Abl tyrosine kinase is essential to the formation of axonal connections in the embryonic central nervous system and for attachment of embryonic muscles to the body wall. Molecular isolation and analysis of the genes identified by these second-site mutations should define the molecular basis for the genetic redundancy.

Alleles↗
PubMedDate not supplied

dpp induces mesodermal gene expression in Drosophila.

Inductive interactions between germ layers are an essential feature of the development of many organisms. In several species these interactions are mediated by members of the transforming growth factor-beta (TGF beta) family. In amphibians, different concentrations of activin can induce different types of mesoderm in the animal cap assay. In Drosophila, a member of the TGF beta family, decapentaplegic (dpp), acts as an inductive signal. Midway through embryogenesis, dpp is expressed in the visceral mesoderm, and enhances the expression of the homeotic gene labial in the underlying midgut endoderm. Earlier in development, however, dpp expression is limited to the dorsal ectoderm. At this stage in development, thickveins, a dpp receptor, is expressed in the mesoderm, and this suggests that ectodermal dpp might not only be required for development of dorsal ectoderm, but could also act inductively to mediate pattern formation in the underlying mesoderm. Here we show, by expressing dpp ectopically in the ectoderm and mesoderm and by examining dpp null mutant embryos, that dpp regulates expression of mesodermal genes.

Animals↗