Rajakannan V, Yamane T, Shirai T, Kobayashi T, Ito S, Velmurugan D
Department of Crystallography and Biophysics, University of Madras, Guindy Campus, Chennai - 600 025, India.
J Synchrotron Radiat. 2004 Jan 1;11(Pt 1):64-7. doi: 10.1107/s0909049503023537. Epub 2003 Nov 28.
One of the main interests in the molecular biosciences is in understanding structure-function relations and X-ray crystallography plays a major role in this. ACORN can be used as a comprehensive and efficient phasing procedure for the determination of protein structures when atomic resolution data are available. An initial model can automatically be built by ARP/wARP followed by REFMAC for refinement. The alpha helices and beta sheets occurring in many protein structures can be taken as starting fragments for structure solution in ACORN. ACORN, along with ARP/wARP followed by REFMAC, can be an ab initio method for solving protein structure for which data are better than 1.2 A (atomic resolution). Attempts are here made in extending its applications to real data at 1.45 A resolution and also to truncated data at 1.6 A resolution. Two previously known structures, congerin II and alkaline cellulase N257, were resolved using the above approach. Automatic structure solution, phasing and refinement for real data at still lower resolutions for proteins of various complexities are being carried out. Data mining of the secondary structural features using PDB is being carried out for this new approach for 'seed-phasing' to ACORN.
分子生物科学的主要研究兴趣之一在于理解结构 - 功能关系，而X射线晶体学在这方面发挥着重要作用。当有原子分辨率数据时，ACORN可作为一种全面且高效的相位确定程序用于蛋白质结构的测定。ARP/wARP可自动构建初始模型，随后由REFMAC进行精修。许多蛋白质结构中出现的α螺旋和β折叠可作为ACORN中结构解析的起始片段。ACORN与ARP/wARP随后接REFMAC一起，可作为一种从头开始求解蛋白质结构的方法，适用于数据优于1.2埃（原子分辨率）的情况。本文尝试将其应用扩展到1.45埃分辨率的实际数据以及1.6埃分辨率的截断数据。使用上述方法解析了两个先前已知的结构，即海鳗精蛋白II和碱性纤维素酶N257。正在针对各种复杂程度的蛋白质在更低分辨率下的实际数据进行自动结构解析、相位确定和精修。正在利用蛋白质数据库（PDB）对二级结构特征进行数据挖掘，以用于ACORN的这种新的“种子相位”方法。
