Structural and Functional Characterization of an Ancient Bacterial Transglutaminase Sheds Light on the Minimal Requirements for Protein Cross-Linking.

Transglutaminases are best known for their ability to catalyze protein cross-linking reactions that impart chemical and physical resilience to cellular structures. Here, we report the crystal structure and characterization of Tgl, a transglutaminase from the bacterium Bacillus subtilis. Tgl is produced during sporulation and cross-links the surface of the highly resilient spore.

Auto-induction and purification of a Bacillus subtilis transglutaminase (Tgl) and its preliminary crystallographic characterization.

Spores of Bacillus subtilis are covered by a multi-protein protective coat which is a key factor in their extreme environmental resilience. A fraction of the coat proteins undergoes covalent cross-linking following their assembly at the spore surface. Several types of covalent cross-links are found in the coat.

A left-handed RNA double helix bound by the Z alpha domain of the RNA-editing enzyme ADAR1.

The A form RNA double helix can be transformed to a left-handed helix, called Z-RNA. Currently, little is known about the detailed structural features of Z-RNA or its involvement in cellular processes. The discovery that certain interferon-response proteins have domains that can stabilize Z-RNA as well as Z-DNA opens the way for the study of Z-RNA.

The crystal structure of the Zbeta domain of the RNA-editing enzyme ADAR1 reveals distinct conserved surfaces among Z-domains.

The Zalpha domains represent a growing subfamily of the winged helix-turn-helix (HTH) domain family whose members share a remarkable ability to bind specifically to Z-DNA and/or Z-RNA. They have been found exclusively in proteins involved in interferon response and, while their importance in determining pox viral pathogenicity has been demonstrated, their actual target and biological role remain obscure. Cellular proteins containing Zalpha domains bear a second homologous domain termed Zbeta, which appears to lack the ability to bind left-handed nucleic acids.

Sulfate respiration in Desulfovibrio vulgaris Hildenborough. Structure of the 16-heme cytochrome c HmcA AT 2.5-A resolution and a view of its role in transmembrane electron transfer.

The crystal structure of the high molecular mass cytochrome c HmcA from Desulfovibrio vulgaris Hildenborough is described. HmcA contains the unprecedented number of sixteen hemes c attached to a single polypeptide chain, is associated with a membrane-bound redox complex, and is involved in electron transfer from the periplasmic oxidation of hydrogen to the cytoplasmic reduction of sulfate. The structure of HmcA is organized into four tetraheme cytochrome c(3)-like domains, of which the first is incomplete and contains only three hemes, and the final two show great similarity to the nine-heme cytochrome c from Desulfovibrio desulfuricans.

Spore-coat laccase CotA from Bacillus subtilis: crystallization and preliminary X-ray characterization by the MAD method.

Bacterial endospores are highly resistant structures that allow survival for long periods of time in adverse environments. The spore-forming Gram-positive bacterium Bacillus subtilis synthesizes a coat around the endospore during development composed of several assembled polypeptides. The role of these components of the spore coat remains unclear; however, some of them appear to be enzymes possibly involved in the assembly process or in the final properties of the spore.