Month: September 2022

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

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

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

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

CHAINMAIL AND CEMENT. "In HK97 itself, the intersubunit contacts are reinforced by a post-assembly covalent linkage—an isopeptide bond between adjacent gp5 subunits, so positioned that the entire capsid is topologically interlinked in a ‘chainmail’ arrangement. In other cases, such as bacteriophage λ, the non-covalent interactions between the subunits are reinforced by an additional ‘cement’ protein, which binds on the outer surface of the capsid at positions close to those of the isopeptide bonds in HK97." https://elifesciences.org/content/2/e01299 View in LinkedIn

SO ENDS this first weekend of postings about the most common protein fold on planet earth. No surprises that such an innovation came from viruses, which are so quickly evolving and numerous, that they have generated vast varieties of genetic and structural molecules that have been incorporated into all life forms. And there are still those who believe that viruses are not alive, and simply cannot recognize an alternative and innovative life format. View in LinkedIn

VIRAL ORIGIN. "Recent emergence of numerous lncRNAs suggests that they continue to be actively synthesized (i) from ancestral genes that have lost their coding potential, (ii) by genes or other lncRNAs duplication, transposition, and mutation and (iii) de novo from intergenic DNA." (lncRNA = long non-coding RNA). https://lnkd.in/d2sxUZQ View in LinkedIn

ALL OF EVERYTHING. "The complex genetic phenomena like interference, gene silencing, imprinting, cosuppression, methylation, acetylation, position effect related variegation, transvection and paramutation are hypercyclically interconnected pathways through which ncRNA signalling is affected." (ncRNA = non-coding RNA). View in LinkedIn

Ref for uncted quote: Non-Coding RNAs: A Dynamic and Complex Network of Gene Regulation" "Munshi A, Mohan V and Ahuja YR View in LinkedIn

DYSFUNCTION AND DISEASE. "Because lncRNAs are involved in various and important physiological processes, their dysfunction should have important consequences for cell homeostasis." (lncRNA = long non-coding RNA). https://lnkd.in/d2sxUZQ View in LinkedIn