GBP28 is a novel human plasma gelatin-binding protein that is encoded by apM1 mRNA, expressed specifically in adipose tissue. Three overlapping clones (two lambda clones and one BAC clone) containing the human plasma gelatin-binding protein (GBP28) gene were isolated and characterized. The GBP28 gene spans 16kb and is composed of three exons from 18bp to 4277bp in size with consensus splice sites. The sizes of the two introns were 0.8 and 12kb, respectively. The gene's regulatory sequences contain putative promoter elements, but no typical TATA box. The third exon of this gene contains a long 3'-untranslated sequence containing three Alu repeats. The exon-intron organization of this gene was very similar to that of obese gene, encoding leptin. We also report the chromosome mapping of this gene by fluorescence in situ hybridization (FISH) using a genomic DNA fragment as a probe. The GBP28 gene was located on human chromosome 3q27. The nucleotide sequence data reported in this paper will appear in the DDBJ/EMBL/GenBank nucleotide sequence databases with the accession numbers ABO12163, ABO12164 or ABO12165.