Lysine

Lysine (abbreviated as Lys or K), encoded by the codons AAA and AAG) is an ɑ-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group (which is in the protonated -+NH3 form under biological conditions), an α-carboxylic acid group (which is in the deprotonated –COO- form under biological conditions), and a side chain lysyl ((CH₂)₄NH₂), classifying it as a charged(at physiological pH), aliphatic amino acid. It is essential in humans, meaning the body cannot synthesize it and thus it must be obtained from the diet.

Lysine is a base, as are arginine and histidine. The ε-amino group often participates in hydrogen bonding and as a general base in catalysis. (The ε-amino group (NH₃⁺) is attached to the fifth carbon from the α-carbon, which is attached to the carboxyl (C=OOH) group.)

Common posttranslational modifications include methylation of the ε-amino group, giving methyl-, dimethyl-, and trimethyllysine (the latter occurring in calmodulin); also acetylation, sumoylation, ubiquitination, and hydroxylation - producing the hydroxylysine in collagen and other proteins. O-Glycosylation of hydroxylysine residues in the endoplasmic reticulum or Golgi apparatus is used to mark certain proteins for secretion from the cell. In opsins like rhodopsin and the visual opsins (encoded by the genes OPN1SW, OPN1MW, and OPN1LW), retinaldehyde forms a Schiff base with a conserved lysine residue, and interaction of light with the retinylidene group causes signal transduction in color vision (See visual cycle for details). Deficiencies may cause blindness, as well as many other problems due to its ubiquitous presence in proteins.

Lysine (data page)

References

H5N1 genetic structure

H5N1 genetic structure is the molecular structure of the H5N1 virus's RNA.

H5N1 is an Influenza A virus subtype. Experts believe it might mutate into a form that transmits easily from person to person. If such a mutation occurs, it might remain an H5N1 subtype or could shift subtypes as did H2N2 when it evolved into the Hong Kong Flu strain of H3N2.

H5N1 has mutated through antigenic drift into dozens of highly pathogenic varieties, but all currently belonging to genotype Z of avian influenza virus H5N1. Genotype Z emerged through reassortment in 2002 from earlier highly pathogenic genotypes of H5N1 that first appeared in China in 1996 in birds and in Hong Kong in 1997 in humans. The "H5N1 viruses from human infections and the closely related avian viruses isolated in 2004 and 2005 belong to a single genotype, often referred to as genotype Z."

This infection of humans coincided with an epizootic (an epidemic in nonhumans) of H5N1 influenza in Hong Kong’s poultry population. This panzootic (a disease affecting animals of many species especially over a wide area) outbreak was stopped by the killing of the entire domestic poultry population within the territory. The name H5N1 refers to the subtypes of surface antigens present on the virus: hemagglutinin type 5 and neuraminidase type 1.