One of the possible geometries for zinc in proteins is tetrahedral. Tetrahedral geometry occurs when the central atom is surrounded by four ligands with around 109� between each ligand. This angle will, of course, vary slightly with the ligands on the central atom.
Nuclear receptor assembly (2nll)
Adenovirus-DNA binding protein (1anv)
| This enzyme plays many important roles in adenovirus DNA replication. It protects the displaced single-stranded DNA from nuclease digestion. It also increases the rate and processivity of chain lengthening by DNA polymerase. One final role stems from the helix destablizing properties of the enzyme. | This is important in DNA unwinding. 1anv contains two domains: a c-terminal domain and a smaller n-terminal domain.2 The zinc center is also surrounded by four cysteine groups, connected to the zinc through a sulfur atom. The average bond distance is somewhat short (224 pm) because two of the ligands are bonded closely (215 and 220 pm) to the central zinc. |
Insulin with Clupeine Z (7ins)
| Insulin, an enzyme produced in the beta cells of the liver, is one of the most well known proteins containing zinc. Insulin is important because it regulates the use and storage of food, especially carbohydrates. There are two well known diseases associated with insulin. Diabetes results from the body not producing enough insulin, or not being able to properly use the insulin it does produce. These two problems lead to an increase in blood sugar, which causes many problems, including the buildup of organic acids in liver. Hypoglycemia is caused by an excess of insulin. | This lowers the blood sugar to dangerously low levels. The insulin in this study was cocrystalized with clupeine z. This cocrystalized insulin is important because of its slow release properties after injection.3 The geometry of this center is interesting because it has two "short" bonds to nitrogens (174 and 196 pm) and two "long" bonds, one to a nitrogen (218 pm) and one to an oxygen (216 pm). This is likely due to the large nature of one of the chains (starting with a histidine) extending from the zinc, causing a lengthening in the two bonds to compensate for the crowding. |
Zinc Finger-DNA Complex (1aay)
This zinc center is in a zinc finger. A zinc finger is a DNA-binding protein containing zinc, found in many eukaryotic cells. The protein binds to specific DNA sequences. Some zinc fingers change the structure and unwind DNA upon binding to the strand.4 Zinc fingers participate in regulation of DNA transcription. The zinc is bonded to two nitrogens from histidine groups and two sulfurs from cysteine groups. The average nitrogen bond is 207 pm, while the average sulfur bond is 227 pm.
