de Sanctis Daniele, Dewilde Sylvia, Pesce Alessandra, Moens Luc, Ascenzi Paolo, Hankeln Thomas, Burmester Thorsten, Bolognesi Martino
Department of Physics-INFM and Centre for Excellence in Biomedical Research, University of Genova, Via Dodecaneso 33, Genoa I-16146, Italy.
Biochem Biophys Res Commun. 2004 Apr 16;316(4):1217-21. doi: 10.1016/j.bbrc.2004.03.007.
Cytoglobin is the fourth recognized globin type, almost ubiquitously distributed in human tissues; its function is still poorly understood. Cytoglobin displays a core region of about 150 residues, structurally related to hemoglobin and myoglobin, and two extra segments, about 20 residues each, at the N- and C-termini. The core region hosts a large apolar cavity, held to provide a ligand diffusion pathway to/from the heme, and/or ligand temporary docking sites. Here we report the crystal structure (2.4A resolution, R-factor 19.1%) of a human cytoglobin mutant bearing the CysB2(38) --> Ser and CysE9(83) --> Ser substitutions (CYGB*), treated under pressurized xenon. Three Xe atoms bind to the heme distal site region of CYGB* mapping the protein matrix apolar cavity. Despite the conserved globin fold, the cavity found in CYGB* is structured differently from those recognized to play a functional role in myoglobin, neuroglobin, truncated hemoglobins, and Cerebratulus lacteus mini-hemoglobin.
细胞珠蛋白是第四种被认可的珠蛋白类型，几乎普遍分布于人体组织中；其功能仍知之甚少。细胞珠蛋白显示出一个约150个残基的核心区域，在结构上与血红蛋白和肌红蛋白相关，并且在N端和C端各有一个约20个残基的额外片段。核心区域有一个大的非极性腔，据认为它为进出血红素提供配体扩散途径，和/或作为配体的临时停靠位点。在此我们报告了在加压氙气处理下的一种携带CysB2(38)→Ser和CysE9(83)→Ser替换的人细胞珠蛋白突变体（CYGB*）的晶体结构（分辨率为2.4埃，R因子为19.1%）。三个氙原子结合到CYGB的血红素远端位点区域，描绘出蛋白质基质的非极性腔。尽管具有保守的珠蛋白折叠结构，但在CYGB中发现的腔与那些在肌红蛋白、神经珠蛋白、截短血红蛋白和乳脑纽虫微型血红蛋白中起功能作用的腔结构不同。
