Siderocalin (NGAL; Scn)

Siderocalin (Lipocalin-2, NGAL, 24p3) is a mammalian immune protein of the lipocalin family, playing a vital role in host defense by binding and sequestering iron-chelating siderophores. This activity restricts iron availability to invading bacteria, acting as a bacteriostatic mechanism in the innate immune response. The protein is structurally characterized by a cup-shaped binding domain ("calyx") with three positively charged pockets that accommodate the catecholate groups of siderophores, particularly those like enterobactin from *Escherichia coli* and bacillibactin from *Bacillus anthracis*. Siderocalin can also bind a variety of other ferric complexes and is found in monomeric, dimeric, or trimeric forms in plasma. Its selectivity is defined by shape and charge complementarity with specific bacterial siderophores, and bacteria may evade its binding by chemically modifying their siderophores. Siderocalin is used clinically as a biomarker of kidney injury, and altered levels are associated with infection, inflammation, and cancer prognosis. Although not currently a direct drug target, its mechanism of iron sequestration is a focus of research in antimicrobial and diagnostic development.

Other names

Lipocalin-2NGAL24p3Neutrophil gelatinase-associated lipocalinScn

Sequestration of iron by binding ferric siderophore complexes, inhibiting bacterial iron acquisition Potential anti-infective mechanisms by starving pathogens of iron