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MOST COMMON FOLD ON PLANET. "Most proteins fold like this. By the sheer number of viruses that exist, people estimate this to be the most common fold of a protein on earth. It’s known as the HK97 fold. Viruses with the HK97 fold infect hosts throughout all kingdoms of life, suggesting it’s been around for billions of years." https://lnkd.in/d6j6P8g View in LinkedIn

STRUCTURAL COMMONALITY. "Structural comparison of the major subunits of viral capsids suggests common origins for viruses that infect hosts from different domains of life. One such viral structure-based lineage is the HK97-like group." http://www.sciencedirect.com/science/article/pii/S0042682215001920 View in LinkedIn

LIMITED VIRAL LINEAGES. "Viruses have a crucial role in controlling the evolution of cellular organisms owing to their high abundance and genetic diversity. However, cryoelectron microscopic and crystallographic studies have revealed that this genetic diversity may be reduced to a limited number of structure-based viral lineages." https://lnkd.in/dmGjENv View in LinkedIn

VIRAL PARASITES. "Every organism is constantly under the attack of viral infections because viruses outnumber cellular organisms by at least an order of magnitude. It has been estimated that viruses kill approximately one fifth of the marine biomass on a daily basis. Furthermore, viruses are the leading cause of infectious diseases." But the vast majority of viruses are benign. https://lnkd.in/dmGjENv 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-BACTERIAL HYBRIDS. "Many phage genomes are integrated into bacterial chromosomes (prophages) with some species harboring as many as 20 prophages." http://www.sciencedirect.com/science/article/pii/S0042682215001920 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

MOST ABUNDANT ON EARTH. "Viruses, in particular the tailed bacteriophages (Caudovirales), are by far the most abundant biological entities in the biosphere. Phages outnumber bacteria by a factor of ten with an estimated 10(31) virus particles on Earth." https://lnkd.in/dXvJFtt 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

“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