Habash Jarjis, Helliwell John R, Raftery James, Cianci Michele, Rizkallah Pierre J, Chayen Naomi E, Nneji Gwen A, Zagalsky Peter F
Section of Structural Chemistry, Department of Chemistry, University of Manchester, Manchester M13 9PL, England.
Acta Crystallogr D Biol Crystallogr. 2004 Mar;60(Pt 3):493-8. doi: 10.1107/S090744490400037X. Epub 2004 Feb 25.
The blue carotenoprotein alpha-crustacyanin of Homarus gammarus lobster carapace is comprised chemically of five 20 kDa subunits. Only two genes for the proteins have been isolated (J. B. C. Findlay, personal communication) and the five apoproteins fall into two sets of homologous proteins based on their chemical properties (CRTC, consisting of apoproteins C(1), C(2) and A(1), and CRTA, consisting of apoproteins A(2) and A(3)). The diffraction quality of apo C(2) has been improved from 2.2 to 1.3 A and its structure solved. The structure is compared with the A(1) and C(1) proteins determined at 1.4 A [Cianci et al. (2001), Acta Cryst. D57, 1219-1229] and 1.15 A, respectively [Gordon et al. (2001), Acta Cryst. D57, 1230-1237] and found to be very similar. Normalized B-factor difference plots per residue of different types were used to try to find chemically modified residues; none were found at these resolutions. It remains possible that the differences between the CRTC proteins result from differences in amidation. By comparison of a crystal grown with glycerol (studied at 1.6 A) and one grown without glycerol (studied at 1.3 A) it was seen that glycerol bound at the astaxanthin site.
螯龙虾外壳的蓝色胡萝卜素蛋白α - 甲壳蓝蛋白在化学上由五个20 kDa的亚基组成。目前仅分离出了该蛋白的两个基因（J. B. C. Findlay，个人交流），根据化学性质，这五个脱辅基蛋白可分为两组同源蛋白（CRTC，由脱辅基蛋白C(1)、C(2)和A(1)组成；CRTA，由脱辅基蛋白A(2)和A(3)组成）。脱辅基蛋白C(2)的衍射质量已从2.2 Å提高到1.3 Å，其结构也已解析。该结构与分别在1.4 Å [Cianci等人（2001年），《晶体学报》D57卷，1219 - 1229页]和1.15 Å [Gordon等人（2001年），《晶体学报》D57卷，1230 - 1237页]解析的A(1)和C(1)蛋白进行了比较，发现非常相似。使用不同类型残基的归一化B因子差异图来试图找到化学修饰的残基；在这些分辨率下未发现任何修饰残基。CRTC蛋白之间的差异仍有可能是由酰胺化差异导致的。通过比较用甘油生长的晶体（在1.6 Å下研究）和未用甘油生长的晶体（在1.3 Å下研究），发现甘油结合在虾青素位点。
