Showing papers by "Alexander N. Glazer published in 2013"
TL;DR: Invariant and single variant residues were identified and were defined as “core” for nitrogenase function and their identification provides the bases for new analyses of the three-dimensional structure and for mutagenesis studies.
Abstract: Amino acid residues critical for a protein's structure-function are retained by natural selection and these residues are identified by the level of variance in co-aligned homologous protein sequences. The relevant residues in the nitrogen fixation Component 1 α- and β-subunits were identified by the alignment of 95 protein sequences. Proteins were included from species encompassing multiple microbial phyla and diverse ecological niches as well as the nitrogen fixation genotypes, anf, nif, and vnf, which encode proteins associated with cofactors differing at one metal site. After adjusting for differences in sequence length, insertions, and deletions, the remaining >85% of the sequence co-aligned the subunits from the three genotypes. Six Groups, designated Anf, Vnf , and Nif I-IV, were assigned based upon genetic origin, sequence adjustments, and conserved residues. Both subunits subdivided into the same groups. Invariant and single variant residues were identified and were defined as “core” for nitrogenase function. Three species in Group Nif-III, Candidatus Desulforudis audaxviator, Desulfotomaculum kuznetsovii, and Thermodesulfatator indicus, were found to have a seleno-cysteine that replaces one cysteinyl ligand of the 8Fe:7S, P-cluster. Subsets of invariant residues, limited to individual groups, were identified; these unique residues help identify the gene of origin (anf, nif, or vnf) yet should not be considered diagnostic of the metal content of associated cofactors. Fourteen of the 19 residues that compose the cofactor pocket are invariant or single variant; the other five residues are highly variable but do not correlate with the putative metal content of the cofactor. The variable residues are clustered on one side of the cofactor, away from other functional centers in the three dimensional structure. Many of the invariant and single variant residues were not previously recognized as potentially critical and their identification provides the bases for new analyses of the three-dimensional structure and for mutagenesis studies.
23 citations
01 Jan 2013
TL;DR: Natural reserves and preserves are protected areas set aside for various purposes: preservation of wilderness and of biodiversity, for scientific research, preservation of specific natural, cultural, or traditional attributes, for sustainable use of resources, and for tourism, and education as discussed by the authors.
Abstract: Natural reserves and preserves are protected areas set aside for various purposes: preservation of wilderness and of biodiversity, for scientific research, preservation of specific natural, cultural, or traditional attributes, for sustainable use of resources, and for tourism, and education. Worldwide, over 100,000 such areas collectively cover ∼12.5% of Earth's land surface. Over 5000 marine protected areas cover ∼1.2% of the area of the oceans. Examples of different types of reserves and preserves are described. Natural areas make many critical contributions to conserving unique habitats, but confront many threats and face an uncertain future in a world undergoing rapid climate change.
6 citations