Lanosterol synthase

Lanosterol synthase is an oxidosqualene cyclase (OSC) enzyme that converts (S)-2,3-oxidosqualene to a protosterol cation and finally to lanosterol.Lanosterol is a key four-ringed intermediate in cholesterol biosynthesis. In humans, lanosterol synthase is encoded by the LSS gene.

In eukaryotes, lanosterol synthase is an integral monotopic protein associated with the cytosolic side of the endoplasmic reticulum. Some evidence suggests that the enzyme is a soluble, non-membrane bound protein in the few prokaryotes that produce it.

Due to the enzyme’s role in cholesterol biosynthesis, there is interest in lanosterol synthase inhibitors as potential cholesterol-reducing drugs, to complement existing statins.

Mechanism

Though some data on the mechanism has been obtained by the use of suicide inhibitors, mutagenesis studies, and homology modeling, it is still not fully understood how the enzyme catalyzes the formation of lanosterol.

Initial epoxide protonation and ring opening

Before the acquisition of the protein’s X-ray crystal structure, site-directed mutagenesis was used to determine residues key to the enzyme’s catalytic activity. It was determined that an aspartic acid residue (D455) and two histidine residues (H146 and H234) were essential to enzyme function. Corey et al. hypothesized that the aspartic acid acts by protonating the substrate’s epoxide ring, thus increasing its susceptibility to intramolecular attack by the nearest double bond, with H146 possibly intensifying the proton donor ability of the aspartic acid through hydrogen bonding. After acquisition of the X-ray crystal structure of the enzyme, the role of D455 as a proton donor to the substrate’s epoxide was confirmed, though it was found that D455 is more likely stabilized by hydrogen bonding from two cysteine residues (C456 and C533) than from the earlier suggested histidine.

Gene

A gene is a locus (or region) of DNA that encodes a functional RNA or protein product, and is the molecular unit of heredity. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. Most biological traits are under the influence of polygenes (many different genes) as well as the gene–environment interactions. Some genetic traits are instantly visible, such as eye colour or number of limbs, and some are not, such as blood type, risk for specific diseases, or the thousands of basic biochemical processes that comprise life.

Genes can acquire mutations in their sequence, leading to different variants, known as alleles, in the population. These alleles encode slightly different versions of a protein, which cause different phenotype traits. Colloquial usage of the term "having a gene" (e.g., "good genes," "hair colour gene") typically refers to having a different allele of the gene. Genes evolve due to natural selection or survival of the fittest of the alleles.

Eugene (given name)

Eugene is a common (masculine) first name that comes from the Greek εὐγενής (eugenēs), "noble", literally "well-born", from εὖ (eu), "well" and γένος (genos), "race, stock, kin".Gene is a common shortened form. The feminine variant is Eugenia or Eugénie.

Male foreign-language variants include:

Notable people

Christianity

Military

Gene (novel)

Gene is a thriller novel by Stel Pavlou (born 1970), published in 2005 in England by Simon & Schuster. It is published in several languages with some title changes. The Italian edition has the title La Conspirazione del Minotauro (The Minotaur Conspiracy). The novel is about a fictional New York detective, James North, who in the process of hunting down a criminal, uncovers a genetics experiment to unlock past lives through genetic memory, therefore achieving a kind of immortality. In so doing North discovers his own origins, that of a soldier from the Trojan War who is reincarnated seven times through history, forced to confront his nemesis each time, all for the loss of his one true love.

Characters

Cyclades (born circa 1300 BC)

Incarnations of Cyclades

Athanatos (born circa 1500 BC)

Incarnations of Athanatos

List of most luminous stars

Below is a list of stars arranged in order of decreasing luminosity (increasing bolometric magnitude). Accurate measurement of stellar luminosities is quite difficult in practice, even when the apparent magnitude is measured accurately, for four reasons:

LSS

LSS may refer to: