Volume 9 Issue 9, September 2002

Mechanosensitive ion channels from bacteria open like an iris, with the transmembrane helices tilting into the membrane to make a thin, wide structure with a 3 nm pore.

The structure of TAG, a DNA repair enzyme, reveals how evolutionary changes in the sequence of a conserved scaffold may enrich the mechanistic diversity of the DNA HhH glycosylase superfamily through a unique coupling of catalysis to substrate selectivity.

Molecular chaperones generally assist in the folding of proteins, and the cytoplasmic chaperone Hsp90, with its cofactors, additionally aids the activation of signaling proteins, including nuclear receptors. New evidence suggests that these chaperones also act to disassemble and down-regulate transcriptionally active nuclear receptor complexes.

A second three-dimensional crystal structure of the Ca²⁺-ATPase from the sarcoplasmic reticulum of rabbit muscle has been determined, this time in a Ca²⁺-free state. Its comparison with the previously determined Ca²⁺-bound state reveals details of structural changes at an atomic level in the catalytic cycle of a P-type ATP-dependent cation pump.