Reviews & Analysis

Proteins are the dogmatic workhorses of genetic regulation, able to both sense the presence of small molecules and control gene expression levels. Two recent studies have now shown that RNA molecules can also serve as the 'sensor' components of genetic regulatory circuits.

The crystal structure of the central region of Rad51 bound to a BRC peptide from BRCA2 shows that the BRC peptide mimics a structural motif within Rad51 and can thereby regulate assembly of the Rad51 nucleoprotein filament needed for DNA repair.

The structures of four lysine methyltransferases give us the first glimpse of the molecular architecture responsible for histone/protein lysine methylation, whereas a recent study of the Esa1 histone acetyltransferase suggests that lysine acetyltransferases still have surprises in store.

Histone methylation regulates the transcriptional activity of genes in the chromatin fiber and might provide a mechanistic basis for inheritable epigenetic patterns of gene transcription.

Considerable evidence indicates that the processes involved in synthesizing mature messenger RNA in the eukaryotic nucleus are intimately coupled to one another. RNA polymerase II plays an important role in all of these events, participating in its primary function in transcription as well as in subsequent RNA processing. Unexpectedly, recent studies indicate that RNA processing factors can reciprocate, 'reaching back' in the pathway to influence transcription.

The transition states for folding of a small globular protein S6 and its circular permutant show remarkable plasticity. This finding supports the statistical nature of the folding reaction and the critical role of intrachain connectivity.

Results from in vitro selection studies reveal that enhanced ribozyme stability can be achieved through a small number of substitutions, which primarily improve the packing interactions in the molecular interior.

The atomic resolution structure of a microbial sensory rhodopsin interacting with its cognate transducer protein casts light on signal transmission between two membrane proteins.

dsRNA viruses share similar replicative strategies and the same unusual inner capsid architecture. The fold of the inner capsid protein is not conserved, however.

Two recent studies provide evidence for a direct interaction between the ribosomal protein L23 at the exit tunnel of the ribosome and the bacterial chaperone trigger factor, and between the eukaryotic L23 homolog and the signal recognition particle. These findings indicate that the exit site of the ribosome may physically link translation to the cytosolic components that guide nascent polypeptides to their correct fate.

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.

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.

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.

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.

CheZ is a protein involved in signal transduction in bacterial chemotaxis and accelerates the dephosphorylation of the activated response regulator, CheY-phosphate. The crystal structure of CheZ in complex with activated CheY provides insights into the function of CheZ.

An example of crosstalk between 'tails' of different histones within nucleosomes suggests novel mechanisms of chromatin regulation.

NMR spectra recorded on the 900 kDa GroEL–GroES complex substantially raise the bar for the size of macromolecules that can be studied by NMR techniques.

Desmoplakin is a major and essential constituent of the interface between the transmembrane glycoproteins mediating adhesion and the intermediate filament cytoskeleton in the cell interior. The structures of two desmoplakin domains that participate in intermediate filament binding reveal that a unique 38-amino acid repeat-containing domain shared with related proteins packs in a novel globular fold.

The structural comparison of a Gag fragment comprising matrix and the N-terminal domain of capsid with mature matrix and capsid provides insight into the structural rearrangement upon viral maturation. Proteolytic cleavage of Gag triggers β-hairpin formation in capsid.