Characterization of the murine gene of gC1qBP, a novel cell protein that binds the globular heads of C1q, vitronectin, high molecular weight kininogen and factor XII

Abstract

gC1qBP is a novel cell protein which was found to interact with the globular heads of C1q, high mol. wt kininogen, factor XII and the heparin-binding, multimeric form of vitronectin. The protein sequence shows no homology to any protein family. This paper describes the genomic organization of mouse gC1qBP and the characterization of its 5′ flanking region. The mouse gene consists of six exons separated by five introns, and its total length is approximately 6 kb. Exon 1 encodes the putative signal peptide, a long stretch of 70 amino acid residues, and the first four amino acid residues found in the mature gC1qBP. Exons 2–5 encode four very hydrophilic domains, whereas exon 6 encodes a neutral domain. The amino acid sequence responsible for binding to the heparin-binding, multimeric form of vitronectin is located in exon 2. A 1 kb DNA fragment upstream of the first initiation codon was sequenced, which contained four potential TATA boxes, seven CAAT boxes, six SP1 sites and various putative transcription factor-binding elements, indicating that the promoter region is in close proximity to the first exon. The mouse C1qbp gene was mapped to chromosome 11, closely linked to D11Mit4 using genomic DNAs from a (C57BL/6J× Mus spretus)F 1× Mus spretus backcross.