To achieve de novo protein structure determination of challenging cases, multi-wavelength anomalous diffraction(MAD) and multiple isomorphous replacement(MIR) phasing can be powerful tools to obtain low-resolution ini...To achieve de novo protein structure determination of challenging cases, multi-wavelength anomalous diffraction(MAD) and multiple isomorphous replacement(MIR) phasing can be powerful tools to obtain low-resolution initial phases from heavy-atom derivative datasets, then phase extension is needed against high-resolution data to obtain accurate structures.In this context, we propose a direct-methods procedure here that could improve the initial low-resolution MAD/MIR phase quality.And accordingly, an automated process for extending initial phases to high resolution is also described.These two procedures are both implanted in the newly released IPCAS pipeline.Three cases are used to perform the test, including one set of 4.17 ? MAD data from a membrane protein and two sets of MAD/MIR data with derivatives truncated down to 6.80 ? and 6.90 ?, respectively.All the results have shown that the initial phases generated from the direct-methods procedure are better than that from the conventional MAD/MIR methods.The automated phase extensions for the latter two cases starting from 6.80 ? to 3.00 ? and 6.90 ? to 2.80 ? are proved to be successful, leading to complete models.This may provide convenient and reliable tools for phase improvement and phase extension in difficult low-resolution tasks.展开更多
The cephalosporin acylases are a group of enzymes that hydrolyze cephalosporin C and/or glutaryl 7 aminocephalosporanic acid to produce 7 aminocephalosporanic acid. The cephalosporin acylase from Pseudomonas sp. ...The cephalosporin acylases are a group of enzymes that hydrolyze cephalosporin C and/or glutaryl 7 aminocephalosporanic acid to produce 7 aminocephalosporanic acid. The cephalosporin acylase from Pseudomonas sp. strain 130 was crystallized in two different forms suitable for structural studies. A tetragonal crystal form diffracted to 0.24 nm belonged to the space group P4 12 12. There was one αβ heterodimer per asymmetric unit. A second crystal form diffracted to 0.21 nm belonged to the space group P2 1. There was four αβ heterodimers per asymmetric unit. The tetragonal crystal structure of CA 130 was determined using the multiwavelength anomalous diffraction method and the P2 1 crystal structure was then determined using the molecular replacement method.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2011CB911100)of the Ministry of Science and Technology of China
文摘To achieve de novo protein structure determination of challenging cases, multi-wavelength anomalous diffraction(MAD) and multiple isomorphous replacement(MIR) phasing can be powerful tools to obtain low-resolution initial phases from heavy-atom derivative datasets, then phase extension is needed against high-resolution data to obtain accurate structures.In this context, we propose a direct-methods procedure here that could improve the initial low-resolution MAD/MIR phase quality.And accordingly, an automated process for extending initial phases to high resolution is also described.These two procedures are both implanted in the newly released IPCAS pipeline.Three cases are used to perform the test, including one set of 4.17 ? MAD data from a membrane protein and two sets of MAD/MIR data with derivatives truncated down to 6.80 ? and 6.90 ?, respectively.All the results have shown that the initial phases generated from the direct-methods procedure are better than that from the conventional MAD/MIR methods.The automated phase extensions for the latter two cases starting from 6.80 ? to 3.00 ? and 6.90 ? to 2.80 ? are proved to be successful, leading to complete models.This may provide convenient and reliable tools for phase improvement and phase extension in difficult low-resolution tasks.
基金Supported by the National Natural Science Foundation (No. 39970 15 5 ) the High- Technology Developm entProgram of China (No. 2 0 0 1AA2 330 11) +1 种基金and theNational Frontier Research Program (No.G19990 75 6 0 2 G19990 1190 2 and19980 5 110 5 )
文摘The cephalosporin acylases are a group of enzymes that hydrolyze cephalosporin C and/or glutaryl 7 aminocephalosporanic acid to produce 7 aminocephalosporanic acid. The cephalosporin acylase from Pseudomonas sp. strain 130 was crystallized in two different forms suitable for structural studies. A tetragonal crystal form diffracted to 0.24 nm belonged to the space group P4 12 12. There was one αβ heterodimer per asymmetric unit. A second crystal form diffracted to 0.21 nm belonged to the space group P2 1. There was four αβ heterodimers per asymmetric unit. The tetragonal crystal structure of CA 130 was determined using the multiwavelength anomalous diffraction method and the P2 1 crystal structure was then determined using the molecular replacement method.
