STRUCTURAL ORGANIZATION OF THE GENE ENCODING THE HUMAN LIPOCALIN TEAR PREALBUMIN AND SYNTHESIS OF THE RECOMBINANT PROTEIN IN ESCHERICHIA-COLI

The genomic DNA fragment encoding the human lipocalin tear prealbumin (LCN1), a new member of the superfamily of hydrophobic molecule transporters, has been isolated and sequenced. The entire gene is approximately 6.2 kb in size and contains six protein-coding exons and a 3'-nontranslated exon. All exon/intron splice junctions exactly follow the GT/AG rule. The structure of the LCN1 gene is highly similar, in terms of numbers and sizes of exons and in intron phasing to that of the genes encoding ovine beta-lactoglobulin, human placental protein P14, rat alpha 2-urinary globulin, rat prostaglandin D synthase and human alpha 1-microgobulin, thus supporting the close evolutionary relationship of these genes. The 5'-noncoding region of LCN1 contains, besides a TATA and CAAT box, several motifs that resemble regulatory elements of other eukaryotic genes, including potential metal-responsive elements (MRE) and a cAMP-responsive element (CRE). As a basis for further investigations concerning the structure-function relationship and to generate a source of recombinant protein for X-ray crystallography studies, LCN1 was produced in Escherichia coli as a fusion with maltose-binding protein.