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Structure. 2014 Jun 10;22(6):830-41. doi: 10.1016/j.str.2014.04.003. Epub 2014 May 15.

Multiple functional roles of the accessory I-domain of bacteriophage P22 coat protein revealed by NMR structure and CryoEM modeling.

Author information

1
Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA.
2
Verna and Marrs McLean Department of Biochemistry and Molecular Biology, National Center for Macromolecular Imaging, Baylor College of Medicine, Houston, TX 77030, USA.
3
Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
4
Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA. Electronic address: andrei.alexandrescu@uconn.edu.
5
Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, USA; Department of Chemistry, University of Connecticut, Storrs, CT 06269, USA. Electronic address: teschke@uconn.edu.

Abstract

Some capsid proteins built on the ubiquitous HK97-fold have accessory domains imparting specific functions. Bacteriophage P22 coat protein has a unique insertion domain (I-domain). Two prior I-domain models from subnanometer cryoelectron microscopy (cryoEM) reconstructions differed substantially. Therefore, the I-domain's nuclear magnetic resonance structure was determined and also used to improve cryoEM models of coat protein. The I-domain has an antiparallel six-stranded β-barrel fold, not previously observed in HK97-fold accessory domains. The D-loop, which is dynamic in the isolated I-domain and intact monomeric coat protein, forms stabilizing salt bridges between adjacent capsomers in procapsids. The S-loop is important for capsid size determination, likely through intrasubunit interactions. Ten of 18 coat protein temperature-sensitive-folding substitutions are in the I-domain, indicating its importance in folding and stability. Several are found on a positively charged face of the β-barrel that anchors the I-domain to a negatively charged surface of the coat protein HK97-core.

PMID:
24836025
PMCID:
PMC4068711
DOI:
10.1016/j.str.2014.04.003
[Indexed for MEDLINE]
Free PMC Article

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