5jbl
From Proteopedia
Structure of the bacteriophage T4 capsid assembly protease, gp21.
Structural highlights
FunctionPCPP_BPT4 The pathway of bacteriophage T4 head assembly begins with the formation of a prohead bound to the bacterial cell membrane which is later converted to the mature, DNA-containing head. During maturation, all but one of the prohead proteins are proteolytically processed by a phage-coded protease which is formed by autocatalytic cleavage of the product of gene 21 (gp21). Protease gp21 has been tentatively located in the center of the prohead core. Publication Abstract from PubMedMany large viruses, including tailed dsDNA bacteriophages and herpesviruses, assemble their capsids via formation of precursors, called procapsids or proheads. The prohead has an internal core, made of scaffolding proteins, and an outer shell, formed by the major capsid protein. The prohead usually contains a protease, which is activated during capsid maturation to destroy the inner core and liberate space for the genome. Here, we report a 2.0 A resolution structure of the pentameric procapsid protease of bacteriophage T4, gene product (gp)21. The structure corresponds to the enzyme's pre-active state in which its N-terminal region blocks the catalytic center, demonstrating that the activation mechanism involves self-cleavage of nine N-terminal residues. We describe similarities and differences between T4 gp21 and related herpesvirus proteases. We found that gp21 and the herpesvirus proteases have similarity with proteins forming the tubes of phage tails and bacterial type VI secretion systems, suggesting their common evolutionary origin. Common Evolutionary Origin of Procapsid Proteases, Phage Tail Tubes, and Tubes of Bacterial Type VI Secretion Systems.,Fokine A, Rossmann MG Structure. 2016 Nov 1;24(11):1928-1935. doi: 10.1016/j.str.2016.08.013. Epub 2016, Sep 22. PMID:27667692[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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