Today's fold

The whole set

Today's pick is drawn from this small, curated set — not from 200+ million entries. Open any of them:

• p53 P04637 — A tumour-suppressor protein that helps a cell pause to repair its DNA — or self-destruct when the damage is too great. Its gene is mutated in a large fraction of human cancers, which is why it is one of the most-studied proteins in biology.
• Haemoglobin β P68871 — One of the four subunits of haemoglobin, the molecule that ferries oxygen in red blood cells. A single amino-acid change in this subunit is the classic example of a point mutation, the one behind sickle-cell disease.
• Insulin P01308 — The hormone that signals cells to take up glucose from the blood after a meal. It was the first protein to have its complete amino-acid sequence worked out.
• Green fluorescent protein P42212 — A jellyfish protein that glows green under blue light. Biologists borrowed it as a tag to see when and where other proteins appear inside living cells.
• SARS-CoV-2 spike P0DTC2 — The surface protein that the SARS-CoV-2 virus uses to latch onto and enter human cells. It is the piece the first COVID-19 vaccines were designed around.
• EGFR P00533 — A receptor that sits in the cell membrane and signals the cell to grow and divide when it binds its growth factor. It is a well-known drug target in several cancers.
• Myoglobin P02144 — An oxygen-storing protein that gives muscle its red colour. This is the human one. The first protein structure ever solved by X-ray crystallography, in 1957–58, was a sperm whale's myoglobin.
• Calmodulin P0DP23 — A small sensor protein that binds calcium and then switches many other proteins on or off. It is a central relay for the calcium signals a cell uses to make decisions.
• CFTR P13569 — A channel that moves chloride ions across cell membranes to keep surface fluids balanced. The loss of a single residue, ΔF508, is the most common change seen in cystic fibrosis.
• ABL1 kinase P00519 — An enzyme that attaches phosphate groups to other proteins to pass along growth signals. A gene fusion that leaves it stuck 'on' is associated with chronic myeloid leukaemia.
• BRCA1 P38398 — A protein that helps a cell repair double-strand breaks in its DNA. Certain inherited variants in its gene are linked to a higher lifetime risk of breast and ovarian cancer.
• Serum albumin P02768 — The most abundant protein in blood plasma. It acts as a molecular taxi, carrying hormones, fatty acids and many drugs around the body.
• Hemoglobin (alpha) P69905 — Hemoglobin is the red stuff in your blood. Oxygen sticks to it in your lungs and comes off again out in your body.
• Alpha-amylase P0DUB6 — This enzyme in your spit chops starch into sugar. That is why bread starts to taste sweet if you chew it for a while.
• Antibody (IgG) P01857 — Antibodies are Y-shaped grabbers your blood makes to catch germs. They lock onto a germ and flag it for the cleanup team.
• Collagen P02452 — Collagen is the rope that holds your skin, tendons, and bones together. It is the most common protein in your body.
• Keratin P04264 — Keratin builds your hair, fingernails, and the top layer of your skin. It is tough because its chains stack tightly.
• Actin P68133 — Actin links into long cables inside muscle cells. When myosin pulls on those cables, your muscle squeezes shorter.
• Myosin P12882 — Myosin is a tiny motor inside muscle. Each time it uses up a bit of fuel called ATP, it changes shape and tugs on actin cables. Millions of tugs make a muscle squeeze.
• Trypsin P07477 — Trypsin lives in your small intestine. It snips proteins from food into smaller chunks your gut can use.
• Pepsin P0DJD7 — Pepsin works in your stomach where the acid is strong. It starts breaking down protein in food right away.
• Lactase P09848 — Lactase splits the sugar in milk into two smaller sugars. Many people make much less of it after childhood, and then a lot of milk can upset their stomach.
• Catalase P04040 — Your cells make a chemical called hydrogen peroxide that can hurt them. Catalase chops it into water and oxygen, fast.
• Lysozyme P61626 — Lysozyme is in your tears, spit, and snot. It pops open the walls of bacteria before they can make you sick.
• Ferritin P02794 — Ferritin is a hollow ball that stores iron safely inside your cells until your body needs it.
• Casein P02662 — Casein is the main protein in cow milk. Its tiny clumps, along with drops of fat, scatter light, so milk looks white.
• Ovalbumin P01012 — Ovalbumin is the main protein in an egg white. When you cook an egg, its shape changes and it turns from clear to white.
• Cytochrome c P99999 — Cytochrome c hands off electrons inside the parts of your cell that make most of its energy. Without it, a cell loses most of its energy supply.
• ATP synthase P06576 — ATP synthase is a real spinning motor inside your cells. Each full turn builds three new pellets of ATP fuel.
• Tubulin Q71U36 — Tubulin snaps together into long hollow tubes. Those tubes are the rails your cell uses to move things around.
• DNA polymerase P09884 — DNA polymerases copy your DNA before a cell splits. This one, polymerase alpha, starts each new piece of the copy. Other polymerases carry the copying on and fix most mistakes.
• RNA polymerase II P24928 — This protein reads a gene in your DNA and writes a matching RNA copy. The cell uses that copy to build a protein.
• Histone H3 P68431 — Histones are spools that DNA wraps around. Without them, your DNA would not fit inside the cell.
• Ribosomal protein S6 P62753 — A ribosome is a tiny factory that builds proteins. S6 is one bolt that holds the factory together.
• CRISPR Cas9 Q99ZW2 — Cas9 is a scissors protein that bacteria use against viruses. Scientists turned it into a tool to edit DNA on purpose.
• ACE2 Q9BYF1 — ACE2 sits on the outside of your cells and helps control blood pressure. It is also where the COVID virus's spike sticks.
• Rhodopsin P08100 — Rhodopsin sits in the back of your eye. When light hits it, it bends, and that bend starts a signal that travels to your brain.
• Aquaporin-1 P29972 — Aquaporins are water channels in the thin membrane around your cells. They let water rush in and out without letting salt or sugar through.
• Dopamine D2 receptor P14416 — This protein catches a brain signal called dopamine. The signal matters for movement and reward.
• Acetylcholinesterase P22303 — Your nerves send a signal called acetylcholine to your muscles. This enzyme chops it back up so the signal turns off.
• Hexokinase P19367 — Hexokinase is the first step when your cell burns sugar for energy. It tags glucose so it cannot escape the cell.
• GLUT4 (glucose transporter) P14672 — GLUT4 is a sugar door on your muscle and fat cells. After you eat, insulin's signal brings more of these doors up to the cell's surface.
• Sodium-potassium pump P05023 — This pump uses fuel to push sodium out of your cell and pull potassium in. Your nerves and muscles need this gap to work.
• Tyrosinase P14679 — Tyrosinase makes the brown pigment in your skin, hair, and eyes. Different gene versions make different amounts.
• Lactoferrin P02788 — Lactoferrin in milk and tears holds on tightly to iron, so germs nearby get less of it. Germs need iron to grow, so this slows them down.
• Beta-lactoglobulin P02754 — This is the main whey protein in cow milk. It is one of the proteins that some people are allergic to.
• Antifreeze protein (type I) P04002 — Some fish in icy water make this protein. It sticks to tiny ice crystals so they cannot grow big enough to hurt the fish.
• Firefly luciferase P08659 — Luciferase is the enzyme that makes a firefly's tail glow. It helps a chemical called luciferin react with oxygen, using ATP fuel, and that reaction gives off light.
• Alpha-crystallin A P02489 — This protein packs tightly into your eye lens so it stays clear. As we get older, it slowly tangles, and lenses can cloud over.
• Hemagglutinin (H1N1 flu) P03452 — Hemagglutinin is the spike on flu viruses. It sticks to cells in your nose and throat, which lets the virus get in.
• RuBisCO P00875 — RuBisCO is how plants take carbon out of the air to build sugar. It is part of the engine of photosynthesis.
• Aldolase A P04075 — Aldolase is a sugar-cutter. It splits a six-carbon sugar in half so your cells can keep pulling energy out of it.
• Growth hormone P01241 — Growth hormone is a signal from a small gland just below your brain. Your body releases most of it during sleep, and it helps you grow taller.