Identification and characterization of 1,25D3-membrane-associated rapid response, steroid (1,25D3-MARRS) binding protein.

1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) operates through pharmacologically distinct nuclear receptor-mediated and plasma membrane-initiated mechanisms. The nuclear receptor is well described, but the membrane receptor identity remains unproven. A 66 kDa protein from chick intestinal basolateral membranes was isolated previously and identified as a candidate receptor (now termed 1,25D(3)-MARRS). A chicken cDNA library was screened for clones encoding the N-terminal sequence of 1,25D(3)-MARRS. An exact match was found with an insert containing an open coding region for the full-length candidate 1,25D(3)-MARRS protein. Analysis reveals a 5' untranslated region, a precursor translation product with methionine start site, a signal peptide and a translation product of 505 amino acids prior to translation termination site. Prosite analysis predicts potential sites for phosphorylation by casein kinase II cAMP-dependent kinase, protein kinase C, and tyrosine kinase and an N-myristoylation site with high probability of occurrence. Additionally, two conserved domains capable of interacting with Rel homology domains (RHD) are present. Oligonucleotide primers sets designed to amplify unique regions of the sequence produced amplimers of the predicted size from both chicken and rat intestinal cells. Transcription-translation produced a protein that was recognized in Western blot analysis by Ab099, a polyclonal antibody recognizing the N-terminus of the 66 kDa MARRS protein.