De Simone Giovanna, Ascenzi Paolo, di Masi Alessandra, Polticelli Fabio
.
Biomol Concepts. 2017 May 24;8(2):105-118. doi: 10.1515/bmc-2017-0013.
Classical all α-helical globins are present in all living organisms and are ordered in three lineages: (i) flavohemoglobins and single domain globins, (ii) protoglobins and globin coupled sensors and (iii) truncated hemoglobins, displaying the 3/3 or the 2/2 all α-helical fold. However, over the last two decades, all β-barrel and mixed α-helical-β-barrel heme-proteins displaying heme-based functional properties (e.g. ligand binding, transport and sensing) closely similar to those of all α-helical globins have been reported. Monomeric nitrophorins (NPs) and α1-microglobulin (α1-m), belonging to the lipocalin superfamily and nitrobindins (Nbs) represent prototypical heme-proteins displaying the all β-barrel and mixed α-helical-β-barrel folds. NPs are confined to the Reduviidae and Cimicidae families of Heteroptera, whereas α1-m and Nbs constitute heme-protein families spanning bacteria to Homo sapiens. The structural organization and the reactivity of the stable ferric solvent-exposed heme-Fe atom suggest that NPs and Nbs are devoted to NO transport, storage and sensing, whereas Hs-α1-m participates in heme metabolism. Here, the structural and functional properties of NPs and Nbs are reviewed in parallel with those of sperm whale myoglobin, which is generally taken as the prototype of monomeric globins.
经典的全α-螺旋球蛋白存在于所有生物中，并分为三个谱系：（i）黄素血红蛋白和单结构域球蛋白，（ii）原球蛋白和球蛋白偶联传感器，以及（iii）截短血红蛋白，呈现3/3或2/2全α-螺旋折叠。然而，在过去二十年中，已经报道了所有具有与全α-螺旋球蛋白密切相似的基于血红素的功能特性（例如配体结合、运输和传感）的β-桶状和混合α-螺旋-β-桶状血红素蛋白。属于脂质运载蛋白超家族的单体嗜硝基蛋白（NPs）和α1-微球蛋白（α1-m）以及嗜硝基结合蛋白（Nbs）代表了呈现全β-桶状和混合α-螺旋-β-桶状折叠的典型血红素蛋白。NPs仅限于异翅目的红蝽科和臭虫科，而α1-m和Nbs构成了从细菌到智人的血红素蛋白家族。稳定的暴露于溶剂的三价铁血红素-Fe原子的结构组织和反应性表明，NPs和Nbs致力于NO的运输、储存和传感，而人α1-m参与血红素代谢。在此，将NPs和Nbs的结构和功能特性与抹香鲸肌红蛋白的结构和功能特性进行平行综述，抹香鲸肌红蛋白通常被视为单体球蛋白的原型。
