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Ultra‑high resolution X‑ray structures of two forms of human recombinant insulin at 100 K

Lisgarten, DR, Palmer, RA, Lobley, CMC, Naylor, CE, Chowdhry, BZ, Al‑Kurdi, ZI, Badwan, AA, Howlin, Brendan, Gibbons, NCJ, Saldanha, JW , Lisgarten, JN and Basak, AK (2017) Ultra‑high resolution X‑ray structures of two forms of human recombinant insulin at 100 K Chemistry Central Journal, 11 (73).

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Abstract

The crystal structure of a commercially available form of human recombinant (HR) insulin, Insugen (I), used in the treatment of diabetes has been determined to 0.92 Å resolution using low temperature, 100 K, synchrotron X-ray data collected at 16,000 keV (λ = 0.77 Å). Refinement carried out with anisotropic displacement parameters, removal of main-chain stereochemical restraints, inclusion of H atoms in calculated positions, and 220 water molecules, converged to a final value of R = 0.1112 and Rfree = 0.1466. The structure includes what is thought to be an ordered propanol molecule (POL) only in chain D(4) and a solvated acetate molecule (ACT) coordinated to the Zn atom only in chain B(2). Possible origins and consequences of the propanol and acetate molecules are discussed. Three types of amino acid representation in the electron density are examined in detail: (i) sharp with very clearly resolved features; (ii) well resolved but clearly divided into two conformations which are well behaved in the refinement, both having high quality geometry; (iii) poor density and difficult or impossible to model. An example of type (ii) is observed for the intra-chain disulphide bridge in chain C(3) between Sγ6–Sγ11 which has two clear conformations with relative refined occupancies of 0.8 and 0.2, respectively. In contrast the corresponding S–S bridge in chain A(1) shows one clearly defined conformation. A molecular dynamics study has provided a rational explanation of this difference between chains A and C. More generally, differences in the electron density features between corresponding residues in chains A and C and chains B and D is a common observation in the Insugen (I) structure and these effects are discussed in detail. The crystal structure, also at 0.92 Å and 100 K, of a second commercially available form of human recombinant insulin, Intergen (II), deposited in the Protein Data Bank as 3W7Y which remains otherwise unpublished is compared here with the Insugen (I) structure. In the Intergen (II) structure there is no solvated propanol or acetate molecule. The electron density of Intergen (II), however, does also exhibit the three types of amino acid representations as in Insugen (I). These effects do not necessarily correspond between chains A and C or chains B and D in Intergen (II), or between corresponding residues in Insugen (I). The results of this comparison are reported.

Item Type: Article
Divisions : Faculty of Engineering and Physical Sciences > Chemistry
Authors :
NameEmailORCID
Lisgarten, DRUNSPECIFIEDUNSPECIFIED
Palmer, RAUNSPECIFIEDUNSPECIFIED
Lobley, CMCUNSPECIFIEDUNSPECIFIED
Naylor, CEUNSPECIFIEDUNSPECIFIED
Chowdhry, BZUNSPECIFIEDUNSPECIFIED
Al‑Kurdi, ZIUNSPECIFIEDUNSPECIFIED
Badwan, AAUNSPECIFIEDUNSPECIFIED
Howlin, BrendanB.Howlin@surrey.ac.ukUNSPECIFIED
Gibbons, NCJUNSPECIFIEDUNSPECIFIED
Saldanha, JWUNSPECIFIEDUNSPECIFIED
Lisgarten, JNUNSPECIFIEDUNSPECIFIED
Basak, AKUNSPECIFIEDUNSPECIFIED
Date : 1 August 2017
Identification Number : 10.1186/s13065-017-0296-y
Copyright Disclaimer : © The Author(s) 2017. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Depositing User : Melanie Hughes
Date Deposited : 09 Aug 2017 12:14
Last Modified : 09 Aug 2017 12:14
URI: http://epubs.surrey.ac.uk/id/eprint/841868

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