Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706, USA.
Proteins. 2010 Mar;78(4):917-31. doi: 10.1002/prot.22617.
The protein from Arabidopsis thaliana gene locus At1g79260.1 is comprised of 166-residues and is of previously unknown function. Initial structural studies by the Center for Eukaryotic Structural Genomics (CESG) suggested that this protein might bind heme, and consequently, the crystal structures of apo and heme-bound forms were solved to near atomic resolution of 1.32 A and 1.36 A, respectively. The rate of hemin loss from the protein was measured to be 3.6 x 10(-5) s(-1), demonstrating that it binds heme specifically and with high affinity. The protein forms a compact 10-stranded beta-barrel that is structurally similar to the lipocalins and fatty acid binding proteins (FABPs). One group of lipocalins, the nitrophorins (NP), are heme proteins involved in nitric oxide (NO) transport and show both sequence and structural similarity to the protein from At1g79260.1 and two human homologues, all of which contain a proximal histidine capable of coordinating a heme iron. Rapid-mixing and laser photolysis techniques were used to determine the rate constants for carbon monoxide (CO) binding to the ferrous form of the protein (k'(CO) = 0.23 microM(-1) s(-1), k(CO) = 0.050 s(-1)) and NO binding to the ferric form (k'(NO) = 1.2 microM(-1) s(-1), k(NO) = 73 s(-1)). Based on both structural and functional similarity to the nitrophorins, we have named the protein nitrobindin and hypothesized that it plays a role in NO transport. However, one of the two human homologs of nitrobindin contains a THAP domain, implying a possible role in apoptosis. Proteins 2010. (c) 2009 Wiley-Liss, Inc.
拟南芥基因座 At1g79260.1 编码的蛋白由 166 个残基组成，其功能未知。中心真核结构基因组学（CESG）的初步结构研究表明，该蛋白可能与血红素结合，因此，apo 和血红素结合形式的晶体结构分别以接近原子分辨率 1.32 A 和 1.36 A 得到解决。从蛋白中血红素的损失率被测量为 3.6 x 10(-5) s(-1)，表明其特异性和高亲和力地结合血红素。该蛋白形成一个紧凑的 10 股β-桶，在结构上与脂类结合蛋白（FABP）和类脂运载蛋白（lipocalin）相似。一类脂类结合蛋白，硝普蛋白（NP），是涉及一氧化氮（NO）转运的血红素蛋白，与 At1g79260.1 蛋白和两种人类同源物都显示出序列和结构相似性，所有这些都包含一个近端组氨酸，能够协调一个血红素铁。快速混合和激光光解技术用于确定一氧化碳（CO）与蛋白亚铁形式结合的速率常数（k'(CO) = 0.23 microM(-1) s(-1)，k(CO) = 0.050 s(-1)）和一氧化氮（NO）与高铁形式结合的速率常数（k'(NO) = 1.2 microM(-1) s(-1)，k(NO) = 73 s(-1)）。基于与硝普蛋白的结构和功能相似性，我们将该蛋白命名为硝基结合蛋白，并假设它在 NO 转运中发挥作用。然而，硝基结合蛋白的两个人类同源物之一含有 THAP 结构域，暗示其在细胞凋亡中可能发挥作用。蛋白质 2010. (c) 2009 Wiley-Liss, Inc.
