Editing Chaperone (protein) (section)

==Bacteriophage==

The [[gene]]s of [[Escherichia virus T4|bacteriophage (phage) T4]] that encode [[protein]]s with a role in determining phage T4 structure were identified using conditional lethal [[mutant]]s.<ref>Edgar RS, Epstein RH. The genetics of a bacterial virus. Sci Am. 1965;212:70-78. doi:10.1038/scientificamerican0265-70</ref> Most of these proteins proved to be either major or minor structural components of the completed phage particle. However among the gene products (gps) necessary for phage assembly, Snustad<ref>Snustad DP. Dominance interactions in Escherichia coli cells mixedly infected with bacteriophage T4D wild-type and amber mutants and their possible implications as to type of gene-product function: catalytic vs. stoichiometric. Virology. 1968;35(4):550-563. doi:10.1016/0042-6822(68)90285-7</ref> identified a group of gps that act [[Catalysis|catalytically]] rather than being incorporated themselves into the phage structure. These gps were gp26, gp31, gp38, gp51, gp28, and gp4 [gene 4 is synonymous with genes 50 and 65, and thus the gp can be designated gp4(50)(65)]. The first four of these six gene products have since been recognized as being chaperone proteins. Additionally, gp40, gp57A, gp63 and gpwac have also now been identified as chaperones.

Phage T4 [[morphogenesis]] is divided into three independent pathways: the head, the tail and the long tail fiber pathways as detailed by Yap and Rossman.<ref name = Yap2014>Yap ML, Rossmann MG. Structure and function of bacteriophage T4. Future Microbiol. 2014;9(12):1319-1327. doi:10.2217/fmb.14.91</ref> With regard to head morphogenesis, chaperone gp31 interacts with the bacterial host chaperone [[GroEL]] to promote proper folding of the major head [[capsid]] protein gp23.<ref name="Marusich1998">Marusich EI, Kurochkina LP, Mesyanzhinov VV. Chaperones in bacteriophage T4 assembly. Biochemistry (Mosc). 1998;63(4):399-406</ref><ref name="Yap2014" /> Chaperone gp40 participates in the assembly of gp20, thus aiding in the formation of the connector complex that initiates head procapsid assembly.<ref name="Marusich1998" /><ref name="Yap2014" /> Gp4(50)(65), although not specifically listed as a chaperone, acts catalytically as a nuclease that appears to be essential for morphogenesis by cleaving packaged DNA to enable the joining of heads to tails.<ref>Benler S, Hung SH, Vander Griend JA, Peters GA, Rohwer F, Segall AM. Gp4 is a nuclease required for morphogenesis of T4-like bacteriophages. Virology. 2020;543:7-12. doi:10.1016/j.virol.2020.01.008</ref>

During overall tail assembly, chaperone proteins gp26 and gp51 are necessary for baseplate hub assembly.<ref name = Leiman2010>Leiman PG, Arisaka F, van Raaij MJ, et al. Morphogenesis of the T4 tail and tail fibers. Virol J. 2010;7:355. Published 2010 Dec 3. doi:10.1186/1743-422X-7-355</ref>  Gp57A is required for correct folding of gp12, a structural component of the baseplate short tail fibers.<ref name = Leiman2010/>

Synthesis of the long tail fibers depends on the chaperone protein gp57A that is needed for the [[protein trimer|trimerization]] of gp34 and gp37, the major structural proteins of the tail fibers.<ref name = Marusich1998/><ref name = Yap2014/> The chaperone protein gp38 is also required for the proper folding of gp37.<ref name=Leiman2010/><ref>Hyman P, van Raaij M. Bacteriophage T4 long tail fiber domains. Biophys Rev. 2018;10(2):463-471. doi:10.1007/s12551-017-0348-5</ref> Chaperone proteins gp63 and gpwac are employed in attachment of the long tail fibers to the tail baseplate.<ref name = Leiman2010/>