The calx-beta motif is present as a tandem repeat in the cytoplasmic domains of Calx Na-Ca exchangers, which are used to expel calcium from cells. This motif overlaps domains used for calcium binding and regulation. The calx-beta motif is also present in the cytoplasmic tail of mammalian integrin-beta4, which mediates the bi-directional transfer of signals across the plasma membrane, as well as in some cyanobacterial proteins. This motif contains a series of beta-strands and turns that form a self-contained beta-sheet [(PUBMED:9294196), (PUBMED:10390612)].

We have cloned Calx, a gene that encodes a Na-Ca exchanger of Drosophila melanogaster. Calx encodes two repeated motifs, Calx-alpha and Calx-beta, that overlap domains required for exchanger activity and regulation. Calx has multiple transcripts in adults, including at least one expressed in the retina. The Calx genomic locus comprises >/=35 kb between the Atpalpha and rudimentary-like genes in chromosomal region 93B. In Xenopus oocytes, microinjected Calx cRNA induces calcium uptake like that of its homolog, the 3Na+-1Ca2+ exchanger of mammalian heart. Implications of Calx-alpha motifs for the mechanism of Na-Ca exchange are discussed.

This information is based on mapping of SMART genomic protein database to KEGG orthologous groups. Percentage points are related to the number of proteins with Calx_beta domain which could be assigned to a KEGG orthologous group, and not all proteins containing Calx_beta domain. Please note that proteins can be included in multiple pathways, ie. the numbers above will not always add up to 100%.