5tjt
T5 bacteriophage major capsid protein - one PB8 hexon
Structural highlights
FunctionCAPSD_BPT5 Major capsid protein that self-associates to form 120 hexamers and 11 pentamers, building the T=13 icosahedral capsid which about 860 Angstroms in diameter. Responsible for its self-assembly into a procapsid. The phage does not need to encode a separate scaffolfing protein because its capsid protein contains the delta domain that carries that function. The capsid gains its final stability through the reorganization of the subunits that takes place upon expansion. DNA encapsidation through the portal triggers capsid expansion and the binding of the decoration protein to the capsid exterior.[1] [2] [3] Publication Abstract from PubMedBacteriophage capsids constitute icosahedral shells of exceptional stability that protect the viral genome. Many capsids display on their surface decoration proteins whose structure and function remain largely unknown. The decoration protein pb10 of phage T5 binds at the centre of the 120 hexamers formed by the major capsid protein. Here we determined the 3D structure of pb10 and investigated its capsid-binding properties using NMR, SAXS, cryoEM and SPR. Pb10 consists of an alpha-helical capsid-binding domain and an Ig-like domain exposed to the solvent. It binds to the T5 capsid with a remarkably high affinity and its binding kinetics is characterized by a very slow dissociation rate. We propose that the conformational exchange events observed in the capsid-binding domain enable rearrangements upon binding that contribute to the quasi-irreversibility of the pb10-capsid interaction. Moreover we show that pb10 binding is a highly cooperative process, which favours immediate rebinding of newly dissociated pb10 to the 120 hexamers of the capsid protein. In extreme conditions, pb10 protects the phage from releasing its genome. We conclude that pb10 may function to reinforce the capsid thus favouring phage survival in harsh environments. High affinity anchoring of the decoration protein pb10 onto the bacteriophage T5 capsid.,Vernhes E, Renouard M, Gilquin B, Cuniasse P, Durand D, England P, Hoos S, Huet A, Conway JF, Glukhov A, Ksenzenko V, Jacquet E, Nhiri N, Zinn-Justin S, Boulanger P Sci Rep. 2017 Feb 6;7:41662. doi: 10.1038/srep41662. PMID:28165000[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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