The reference OMIM entry for this protein is 176870

Alpha-1 microglobulin/bikunin precursor; ambp
Alpha-1 microglobulin; a1m
Protein hc; hcp
Complex-forming glycoprotein heterogeneous in charge inter-alpha-trypsin inhibitor, light chain, included; itil, included; iatil, included
Bikunin, inclu

DESCRIPTION

The alpha-1-microglobulin/bikunin precursor gene (AMBP) codes for a precursor that splits into alpha-1-microglobulin (A1M; formerly protein HC), which belongs to the lipocalin superfamily, and bikunin (ITIL; formerly HI-30, urinary trypsin inhibitor, inhibitor subunit of inter-alpha-(trypsin) inhibitor), which is made up of 2 tandemly arranged protease inhibitor domains and belongs to the superfamily of Kunitz-type protease inhibitors. The bikunin chain is a member of the inter-alpha-inhibitor (ITI) superfamily. It is a light chain that forms a complex with ITI heavy chains (see ITIH1, 147270) and is also present as a free molecule in plasma (summary by Salier et al., 1992).

CLONING

Protein HC and the HI-30 domain of the ITI light chain are encoded as a single polypeptide chain by a unique mRNA, as shown by sequence analysis of cDNA clones independently isolated from 2 cDNA libraries. Traboni and Cortese (1986) isolated and sequenced a full-length AMBP cDNA clone from a human liver library. Protein HC is a 31-kD, single-chain plasma glycoprotein (alpha-1-microglobulin) that appears to be involved in regulation of the inflammatory process (Mendez et al., 1986). It was originally isolated from the urine of a patient with chronic cadmium poisoning. It is normally present as a free form and as a complex with IgA in the blood, spinal fluid, and urine in relatively low concentration but is present in high concentration in the urine of patients with tubular proteinuria and in blood and urine of patients on renal dialysis (Pervaiz and Brew, 1985). The protein, as well as its IgA complex, inhibits neutrophil chemotaxis to endotoxin-activated serum. Inter-alpha-trypsin inhibitor (ITI) is a serine protease inhibitor that can be isolated from plasma and urine as a high and as a low molecular weight form (Hochstrasser et al., 1976). Salier et al. (1987) proposed that inter-alpha-trypsin inhibitor is a multifunctional protein comprised of polypeptide chains that are synthesized in the liver by 2 distinct mRNAs encoding heavy and light chains. The heavy chain (see ITIH1, 147270) contains potential calcium-binding sites and also regions homologous to the proposed reactive site for thiol-proteinase inhibitors. - Reviews Pugia et al. (2007) reviewed the expression and structure of bikunin, as well as its roles in biologic processes and pathophysiologic conditions.

GENE STRUCTURE

Vetr and Gebhard (1990) isolated the human AMBP gene. It contains 10 exons which span 1.3 kb and 9 introns with an aggregate length of about 16.5 kb. The largest intron (6.5 kb) separates exon 6 (coding for the C-terminal sequence of alpha-1-microglobulin) from exon 7 (coding for a linker peptide and the N-terminal peptide of bikunin). Repetitive DNA sequences of the Alu type were found downstream of the polyadenylation site as well as within introns 4 and 6 and upstream of the putative promoter region.

MAPPING

Traboni et al. (1987) mapped the AMBP gene to chromosome 9 by probing DNA from a panel of somatic cell hybrids. By in situ hybridization experiments, Traboni et al. (1989) narrowed the assignment to 9q22.3-q33. Leveillard et al. (1988) defined a RFLP of the ITIL gene. Diarra-Mehrpour et al. (1989) mapped the ITIL gene to 9q32-q33 by in situ hybridization. By in situ hybridization, Salier et al. (1992) mapped the mouse equivalent of AMBP (Intin-4) to mouse chromosome 4 and the Intin-1 and Intin-3 genes to mouse chromos ... More on the omim web site

Subscribe to this protein entry history

June 30, 2020: Protein entry updated
Automatic update: OMIM entry 176870 was added.

Oct. 19, 2018: Additional information
Initial protein addition to the database. This entry was referenced in Bryk and co-workers. (2017).