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Siderocalin (Scn), lipocalin-2, NGAL, 24p3 is a mammalian lipocalin-type protein that can prevent iron acquisition by pathogenic bacteria by binding siderophores, which are iron-binding chelators made by microorganisms. Iron serves as a key nutrient in host-pathogen interactions, and pathogens can acquire iron from the host organism via synthesis and release siderophores such as enterobactin. Siderocalin is a part of the mammalian defence mechanism and acts as an antibacterial agent.〔 Crystallographic studies of Scn demonstrated that it includes a calyx, a ligand-binding domain that is lined with polar cationic groups. Central to the siderophore/siderocalin recognition mechanism are hybrid electrostatic/cation-pi interactions.〔 To evade the host defences, pathogens evolved to produce structurally varied siderophores that would not be recognized by siderocalin, allowing the bacteria to acquire iron.〔 == Iron requirements of host organisms == Organisms require iron for a variety of chemical reactions. Although iron can be found throughout the biosphere, free ferric iron forms insoluble hydroxides at physiological pH, limiting its accessibility in aerobic conditions to living organisms.〔 In order to preserve homeostasis, organisms have evolved specific protein networks, with proteins and receptors translated in accordance with intracellular iron levels.〔 Export and import are supplemented by a cycling process between the ferrous Fe(II) available in the reducing environment of the cell, and ferric Fe(III) found primarily under aerobic conditions. The iron acquisition mechanisms of pathogenic bacteria demonstrate the role of iron as a key component at the interface between pathogens and hosts.〔〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「siderocalin」の詳細全文を読む スポンサード リンク
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