Enzyme Gallery

HIV reverse transcription enzyme

HIV reverse transcription enzyme. Molecular models of the reverse transcriptase enzyme found in HIV (the human immunodeficiency virus). The foreground model shows the helices and arrowed sheets representing the enzyme's shape (secondary structure). The background model shows the 7844 atoms (spheres) of the molecular structure. Reverse transcriptase is an enzyme that is a key part of the process of producing DNA (deoxyribonucleic acid) from the instructions contained in a strand of RNA (ribonucleic acid). Many viruses, including HIV, consist of a core of RNA, and this reverse transcription is how HIV infects human cells. This enzyme is from the HIV-1 form of HIV, the virus that causes AIDS (acquired immune deficiency syndrome)

© LAGUNA DESIGN/SCIENCE PHOTO LIBRARY

Ricin A-chain, artwork C017/3653

Ricin A-chain. Computer artwork showing the enzymatically active A-chain from a molecule of the toxic protein ricin. Ricin comprises two entwined amino acid chains; A (seen here) and B (not shown). The A-chain is toxic, inhibiting protein synthesis in cells and causing cell death. It is carried into cells by the non-toxic B-chain, which is able to bind to the cell surface. Ricin is derived from the seeds of the castor oil plant (Ricinus communis), making it easy to be used as a toxin by bioterrorists. Less than a milligram is enough to kill an adult. Inhaling ricin causes coughing, pulmonary oedema and death. If ingested, it causes gastroenteritis, liver and kidney damage and death from circulatory failure. There is no antidote

© RAMON ANDRADE 3DCIENCIA/SCIENCE PHOTO LIBRARY

Nepenthes: tropical pitcher plant

The insectivorous nepenthes plants are epiphitic plants that grow on the branches of trees common in Australia, the Phillipines and Malaysia. The brightly coloured pitchers, or glass-shaped receptacles, develop at the end of the leaves in shades of red, green or mottled in order to attract small insects such as mosquitoes and ants. These insects supply the nitrogen the plant needs and which is often lacking in the equatorial soil of their habitat. Odorous substances lure the prey into the pitchers where there are thousands of microscopic fibres and a sticky fluid containing a digestive enzyme Research is ongoing to to see whether these liquids can be developed into eco-friendly pesticides

© SHEILA TERRY/SCIENCE PHOTO LIBRARY