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FEW STRUCTURAL CLASSES. “Capsid proteins of non-enveloped viruses fall, so far, into three major structural classes: the β-jellyroll, the HK97 fold, and the fold of dsRNA-virus shell proteins. The RNA bacteriophage MS2 subunits have a fourth structure, not yet found in eukaryotic viruses. The HK97 fold is present not only in a large number of dsDNA bacteriophage capsids, including the T-phages, lambdoid phages, etc, but also in the major capsid protein of eukaryotic herpesviruses." (dsDNA = double stranded DNA). https://lnkd.in/dzrNZSY View in LinkedIn

“BACTERIOPHAGES or phages are the most abundant organisms in the biosphere and they are a ubiquitous feature of prokaryotic existence. A bacteriophage is a virus which infects a bacterium.” https://lnkd.in/dpr-Qhn View in LinkedIn

MULTIPLE FORMATS. "Auxiliary proteins or Δ-domains strictly control assembly of multiple, identical, HK97-like subunits into procapsids with specific icosahedral symmetries, rather than aberrant non-icosahedral structures. Some coat proteins built on the ubiquitous HK97-fold also have accessory domains or loops that impart specific functions, such as increased monomer, procapsid, or capsid stability. (There are) numerous HK97-like coat protein structures that are emerging in the literature (over 40 at time of writing)." https://lnkd.in/dBCqqe2 View in LinkedIn

FRAGMENT FROM NATURE contemplates the most common biological structure on this planet, a particular viral fold used widely as a structural template with phenomenal flexibility. The ingenious combination of structural stability with an enormous capacity to accommodate greatly different sized structures, and the ability to add embellishments that give new functions to parts makes this structure a unique Lego building block across biological Kingdoms. View in LinkedIn

COMPLEX ASSEMBLY. "The HK97 assembly pathway begins with self-assembly of the capsid protein, gp5, into pentamers and hexamers. A protease, gp4, cleaves gp5 at its N-terminus. Attachment of a portal protein, gp3, coupled with conformational changes leads to formation of a prohead or procapsid structure. Further conformational changes and crosslinking of gp5 monomers comprise further capsid maturation and lead to formation of a mature phage head." https://lnkd.in/d9B2fAQ View in LinkedIn

CENTRAL STRUCTURAL UNIT. "For many (if not all) bacterial and archaeal tailed viruses and eukaryotic Herpesvirdae the HK97-fold serves as the major architectural element in icosahedral capsid formation while still enabling the conformational flexibility required during assembly and maturation. Auxiliary proteins or Δ-domains strictly control assembly of multiple, identical, HK97-like subunits into procapsids with specific icosahedral symmetries, rather than aberrant non-icosahedral structures." http://www.sciencedirect.com/science/article/pii/S0042682215001920 View in LinkedIn

CONSIDERABLE STRUCTURAL FLEXIBILITY. “Variations of the HK97-like fold can occur when the basic building blocks are connected in different order. Additionally, extra domains can be inserted at the E-loop or at the ends of the building blocks." http://www.aimspress.com/article/10.3934/biophy.2015.2.200/fulltext.html View in LinkedIn

NO WEAKEST LINK. "Like the armor, chainmail in viruses provides a thin yet durable layer to endure the internal force exerted by the encapsulated dsDNA. In both cases, chainmail may have been developed for its ability to maintain structural integrity. Indeed, unlike Borromean rings, breaking a single ring in a chainmail does not affect the integrity of the whole mail." (dsDNA = double stranded DNA). http://www.aimspress.com/article/10.3934/biophy.2015.2.200/fulltext.html View in LinkedIn

"CHAINMAIL is a system formed by concatenated rings. Chainmail in the form of interlocking rings of metal was used by medieval knights to protect their bodies from external forces in battle. The term protein chainmail was coined to explain how capsid proteins of HK97 form large complexes that behave abnormally under biochemical analyses. Later, the X-ray structure revealed how the polypeptide chains are arranged in the HK97 mature capsid to form concatenated rings." http://www.aimspress.com/article/10.3934/biophy.2015.2.200/fulltext.html View in LinkedIn

BACTERIAL VIRUS. "HK97 is a bacterial virus, bacteriophage, known to infect Escherichia coli and related bacteria. The capsid protein of HK97, gp5, cross-links upon maturation to form a concatenated chain-mail like structure. The bacteriophage undergoes a maturation process upon DNA packaging during which it expands by nearly 5 nm and changes from spherically symmetrical to icosahedrally symmetrical." https://lnkd.in/d9B2fAQ View in LinkedIn