Extending the scope of coiled-coil crystal structure solution by AMPLE through improved ab initio modelling

Thomas, Jens MH ORCID: 0000-0003-0277-8505, Keegan, Ronan M, Rigden, Daniel J ORCID: 0000-0002-7565-8937 and Davies, Owen R (2020) Extending the scope of coiled-coil crystal structure solution by AMPLE through improved ab initio modelling. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY, 76 (Pt 3). pp. 272-284.

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Official URL: http://dx.doi.org/10.1107/s2059798320000443

Abstract

The phase problem remains a major barrier to overcome in protein structure solution by X-ray crystallography. In recent years, new molecular-replacement approaches using ab initio models and ideal secondary-structure components have greatly contributed to the solution of novel structures in the absence of clear homologues in the PDB or experimental phasing information. This has been particularly successful for highly α-helical structures, and especially coiled-coils, in which the relatively rigid α-helices provide very useful molecular-replacement fragments. This has been seen within the program AMPLE, which uses clustered and truncated ensembles of numerous ab initio models in structure solution, and is already accomplished for α-helical and coiled-coil structures. Here, an expansion in the scope of coiled-coil structure solution by AMPLE is reported, which has been achieved through general improvements in the pipeline, the removal of tNCS correction in molecular replacement and two improved methods for ab initio modelling. Of the latter improvements, enforcing the modelling of elongated helices overcame the bias towards globular folds and provided a rapid method (equivalent to the time requirements of the existing modelling procedures in AMPLE) for enhanced solution. Further, the modelling of two-, three- and four-helical oligomeric coiled-coils, and the use of full/partial oligomers in molecular replacement, provided additional success in difficult and lower resolution cases. Together, these approaches have enabled the solution of a number of parallel/antiparallel dimeric, trimeric and tetrameric coiled-coils at resolutions as low as 3.3 Å, and have thus overcome previous limitations in AMPLE and provided a new functionality in coiled-coil structure solution at lower resolutions. These new approaches have been incorporated into a new release of AMPLE in which automated elongated monomer and oligomer modelling may be activated by selecting `coiled-coil' mode.

Item Type:	Article
Uncontrolled Keywords:	AMPLE, coiled-coils, molecular replacement, phasing
Depositing User:	Symplectic Admin
Date Deposited:	19 Mar 2020 09:12
Last Modified:	06 Oct 2023 15:02
DOI:	10.1107/S2059798320000443
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3079590