Academics Andre's Research Biocuriosities Books Graduate School History of Science Hot off the Press Igor's Research Interdisciplinarity Molecule of the Month Open Access Philip's Research Philosophy of Science Physics Physicsworld.com
Backreaction Ceclia's Blog at PHD Comics Cocktail Party Physics Cosmic Variance The Daily Transcript Easternblot Everyday Scientist The Evilutionary Biologist Freelancing Science The Futile Cycle Good Math, Bad Math iMechanica in singulo Incoherently Scattered Ponderings Juniorprof Klara Stefflova Life of a Lab Rat The Loom Metadatta Mixed States Morning Coffee Physics Not Even Wrong Notes from the biomass Notional Slurry OpenScience Project Pharyngula PLoS Blog Ponderings of a fool Recombinants The Sandwalk SciAm Observations ScienceBlogs Scientific Clearing House Shtetl-Optimized Three-toed Sloth Uncertain Principles What's New by Bob Park
Cholesterol has gained a bad reputation in recent years. It is absolutely essential in our lives: it is needed to keep our membranes fluid and it is the raw material used to build a host of important molecules such as vitamin D and steroid hormones. However, elevated levels of cholesterol (for instance from a fat-rich diet) have been linked to the formation of atherosclerosis and heart disease. Today, doctors suggest that a combination of a healthy low-fat diet and exercise will keep these two faces of cholesterol in balance.
Cholesterol is a bulky lipid molecule, composed of four linked rings of carbon decorated with hydrogen atoms and a single oxygen atom. A collection of two dozen enzymes is needed to build cholesterol from simple starting compounds. The enzyme shown here, oxidosqualene cyclase (PDB entry 1w6k), performs the most complicated step in this process. It takes a long thin carbon chain, oxidosqualene, and folds it up, creating the four linked rings. The enzyme structure shown here has the final product lanosterol bound in the active site, shown here in white.
Both oxidosqualene and lanosterol are mostly hydrocarbon, and thus are not very soluble in water. The enzyme solves this problem by sticking to the membrane in microsomes inside the cell. It then can pull oxidosqualene directly out of the membrane, and release lanosterol back there. The structure shown here includes several small lipids, shown in purple, bound on the side of the protein that sticks to the membrane. You can also see one of these lipids slipping up into a tunnel that leads into the active site.
More from David Goodsell here.
Cosmic Zoom Nature to use Creative Commons License on Select Genome Papers
Biocurious is written by Andre Brown and Philip Johnson, since 2005. Content of the weblog is licensed under a Creative Commons Attribution-Share Alike 3.0 License.
