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These researchers have clarified the basic concepts biochemistry, with the help of ribonuclease, and were all rewarded with the Nobel Prize.

Fast and Aggressive

Ribonuclease A, shown above from the PDB file

5rsa

, is an endonuclease, which means that the RNA can cut inside (endo) of the chain. Other

ribonuclease degrade RNA from the extremities, such as' esosoma
which is involved in the degradation of RNA inside cells.

Ribonuclease A binds to the RNA chain in the large pocket that holds the center of the structure (see figure below from the PDB file 1rta) and attacks with a set of amino acids and bases. Ribonuclease A is an aggressive demolition molecular size very quickly after the RNA bases cytosine, or, though more slowly, after those of uracil. In the course of evolution, has become so efficient that belongs to that small group of enzymes whose activity is not limited by their speed of reaction, but the rate of diffusion of the molecules that must degrade.

strong as a rock Ribonuclease A is incredibly stable. For example, in one of the steps to purify the pancreatic ribonuclease A bovine extracts are treated with sulfuric acid and heated to near boiling, the ribonuclease protein is the only survivor. This is not surprising because it is an enzyme secreted by the pancreas and must act in the intestine where the environment is very inhospitable. The stability of ribonuclease A is due in large part to the four disulfide bonds that bind together different parts of the protein chain and help maintain a compact form.

precision cutting

Ribonuclease A is a powerful tool to cut the RNA into pieces, but the cells also need other tools to make some changes to their target RNA. For example, transfer RNA molecules are synthesized

longer than necessary and then must be trimmed to correct length.

The enzyme ribonuclease

Z, shown on the left, shortening the side chain that binds the amino acid. This structure contains the enzyme in its dimeric form (light blue and dark blue) and a stretch of two molecules of transfer RNA (orange).

The

ribonuclease P, which consists of two protein chains and a ribozyme (an enzyme made of RNA), shorten the chain on the other side (not shown here).

The

ribonuclease III, shown below, binds RNA sequences around the double helix and makes some specific cuts, necessary for the operation and regulation of ribosomal RNA and messenger.

explore the structure Ribonuclease A is a molecular machine dangerous to cells because it cuts across the board, which meets each RNA. E 'toxic for the cells to the point that has also been tested as anticancer drug. Unfortunately it proved not only toxic to cancer cells, but also for than normal and therefore its use in chemotherapy has been abandoned. The cells defend themselves by ribonuclease A (shown in blue) synthesizing potent inhibitors like the one shown in green (PDB file 1dfj). These inhibitors bind immediately to any ribonuclease A molecule that is able to enter the cell. The bond is very strong realized due to the large contact surface between the two molecules, because the inhibitor is almost completely wrapped around the ribonuclease.

Note the unusual structure of the inhibitor that has a very symmetrical crown with many portions outside the alpha helix (in red in the picture below) and folds into so many portions beta (Yellow).

's also interesting to note that the structure of the inhibitor is stabilized by interactions between nonpolar amino acid leucine (highlighted with the atoms in the form of small balls) that protrude abundant in the inner portion of the inhibitor between the helices and beta pleated structures as shown in the figure below.

Source: PDB,

proteopedia.