Protein Family Models

Extracellular Ca2+-dependent nuclease YokF from Bacillus subtilis and several other surface-exposed proteins from diverse bacteria are encoded in the genomes in two paralogous forms that differ by a ~45 amino acid fragment, which comprises a novel conserved domain. Sequence analysis of this domain revealed a conserved DxDxDGxxCE motif, which is strikingly similar to the Ca2+-binding loop of the calmodulin-like EF-hand domains, suggesting an evolutionary relationship between them. Functions of many of the other proteins in which the novel domain, named Excalibur (extracellular calcium-binding region), is found, as well as a structural model of its conserved motif are consistent with the notion that the Excalibur domain binds calcium. This domain is but one more example of the diversity of structural contexts surrounding the EF-hand-like calcium-binding loop in bacteria. This loop is thus more widespread than hitherto recognised and the evolution of EF-hand-like domains is probably more complex than previously appreciated [1]. [1]. 12694917. An extracellular calcium-binding domain in bacteria with a. distant relationship to EF-hands.. Rigden DJ, Jedrzejas MJ, Galperin MY;. FEMS Microbiol Lett 2003;221:103-110. (from Pfam)

Date:

2024-08-14

Present in all three domains of cellular life. Four copies in the transcriptional coactivator p100: these, however, appear to lack the active site residues of Staphylococcal nuclease. Positions 14 (Asp-21), 34 (Arg-35), 39 (Asp-40), 42 (Glu-43) and 110 (Arg-87) [SNase numbering in parentheses] are thought to be involved in substrate-binding and catalysis. [1]. 9041650. P100, a transcriptional coactivator, is a human homologue of. staphylococcal nuclease.. Ponting CP;. Protein Sci 1997;6:459-463.. [2]. 9003410. The human EBNA-2 coactivator p100: multidomain organization and. relationship to the staphylococcal nuclease fold and to the. tudor protein involved in Drosophila melanogaster development.. Callebaut I, Mornon JP;. Biochem J 1997;321:125-132. (from Pfam)

Date:

2024-08-14