PT  - JOURNAL ARTICLE
AU  - Michael Fairhead
AU  - Charlotta Preger
AU  - Edvard Wigren
AU  - Claire Strain-Damerell
AU  - Elena Ossipova
AU  - Mingda Ye
AU  - Mpho Makola
AU  - Nicola A. Burgess-Brown
AU  - Helena Persson
AU  - Frank von Delft
AU  - Susanne Gräslund
TI  - Strategies to improve scFvs as crystallization chaperones suggested by analysis of a complex with the human PHD-bromodomain SP140
AID  - 10.1101/767376
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 767376
4099  - http://biorxiv.org/content/early/2019/09/13/767376.short
4100  - http://biorxiv.org/content/early/2019/09/13/767376.full
AB  - Antibody fragments have great potential as crystallization chaperones for structural biology due to their ability to either stabilise targets, trap certain conformations and/or promote crystal packing. Here we present an example of using a single-chain variable fragment (scFv) to determine the previously unsolved structure of the multidomain protein SP140. This nuclear leukocyte-specific protein contains domains related to chromatin-mediated gene expression and has been implicated in various disease states. The structure of two of the domains (PHD-bromodomain) was solved by crystallizing them as a complex with a scFv generated by phage display technology. SP140 maintains a similar overall fold to previous PHD-bromodomains and the scFv CDR loops predominately interact with the PHD, while the framework regions of the scFv makes numerous interactions with the bromodomain. Analysis of our and other complex structures suggest various protein engineering strategies that might be employed to improve the usefulness of scFvs as crystallization chaperones.