Correspondence

The structure of a conserved hairpin loop involved in peptidyl–tRNA recognition by SOS ribosomal subunits has been solved by NMR. The loop is closed by a novel G–C base pair and presents guanine residues for RNA recognition.

Amaranthus caudatus agglutinin contains a novel arrangement of four β-trefoil domains. The sugar-binding site provides specificity for the carcinoma-associated T-antigen disaccharide even when ‘masked’ by other sugars.

NK-lysin is the first representative of a family of sequence related proteins — saposins, surfactant-associated protein B, pore forming amoeba proteins, and domains of acid sphingomyelinase, acyloxyacylhydrolase and plant aspartic proteinases — for which a structure has been determined.

Staurosporine exhibits nanomolar IC₅₀ values against a wide range of protein kinases. The structure of a CDK2 strauroporine complex explains the tight binding of this inhibitor, and suggests features to be exploited in the design of specific inhibitors of CDKs.

Spermadhesins, 12,000–14,000 M_r mammalian proteins, include lectins involved in sperm–egg binding and display a single CUB domain architecture. We report the crystal structures of porcine seminal plasma PSP-I/PSP-II, a heterodimer of two glycosylated spermadhesins, and bovine aSFP at 2.4 Å and 1.9 Å resolution respectively.

RhoA, a ubiquitous intracellular GTPase, mediates cytoskeletal responses to extracellular signals. A 2.1 Å resolution crystal structure of the human RhoA–GDP complex shows unique stereochemistry in the switch I region, which results in a novel mode of Mg2+ binding.

The structure of the N-terminal actin binding domain of human f imbrin offers the first view of an F-actin crosslinking protein and is representative of the conserved actin binding domain found in the largest family of crosslinking proteins. This domain is composed of two calponin homology domains and allows for the mapping of residues implicated in F-actin binding.

The structure and dynamics of the first KH domain of FMR1 — the protein responsible for fragile X syndrome — reveal that an exposed loop is highly flexible despite containing a GxxG motif that is well conserved throughout the KH family. We suggest that this region provides a putative binding surface for RNA recognition.

RasGAPs supply a catalytic residue, termed the arginine finger, into the active site of Ras thereby stabilizing the transition state of the GTPase reaction and increasing the reaction rate by more than one thousand-fold, in good agreement with the structure of the RasṁRasGAP complex.

Combined kinetic and cryo-EM analysis of the R197A mutant of GroEL provides insight into the allosteric switching of GroEL, which is at the heart of the chaperonin mechanism.

The solution structure of the Ras-binding domain (RBD) of Ral guanine-nucleotide exchange factor RalGEF was solved by NMR spectroscopy. The overall structure is similar to that of Raf-RBD, another effector of Ras, although the sequence identity is only 13%. 1SN chemical shifts changes in the complex of RalGEF-RBD with Ras indicate an interaction similar to the intermolecular β-sheet observed for the complex between Ras and Raf-RBD.

Structural comparison of thymidylate kinase complexed with either dTMP or with AZTMP suggests that the low phosphorylation rate of AZTMP is due to an induced P-loop movement.

The three N-terminal zinc fingers of transcription factor IIIA bind in the DNA major groove. Substantial packing interfaces are formed between adjacent fingers, the linkers lose their intrinsic flexibility upon DNA binding, and several lysine side chains implicated in DNA recognition are dynamically disordered.

The crystal structure of the fructose-2,6-bisphosphatase domain trapped during the reaction reveal a phosphorylated His 258, and a water molecule immobilized by the product, fructose-6-phosphate. The geometry suggests that the dephosphorylation step requires prior removal of the product for an ‘associative in-line’ phosphoryl transfer to the catalytic water.

Using a mutant version of E. coli alkaline phosphatase, we succeeded in trapping and determining the structure of the phospho-enzyme intermediate. The X-ray structure also revealed the catalytic water molecule, bound to one of the active site zinc ions, positioned ideally for the apical attack necessary for the hydrolysis of the intermediate.

The 2.8 Å resolution crystal structure of E. coli ornithine transcarbamylase is presented, the first to be reported for the trimeric, anabolic enzyme.

The predicted distribution of globular proteins over folding types in five complete genomes differs from the tendencies observed in known protein structures. The ratio between the number of predicted membrane and globular proteins is conserved.

The Ras-interacting domains of the the protein-kinase Raf and the Ral guanine nucleotide dissociation stimulator, RalGDS, lack extensive sequence similarity, but their overall three-dimensional structures are very similar to each other. Mutational analysis indicated that three residues in the RalGDS domain are critical for its interaction with Ras.

A very short hydrogen bond between an Asp and a phosphate is established in two high resolution structures (0.98 and 1.05 Å). A mutant complex that changes the Asp to an Asn, which forms a normal hydrogen bond, has a similar free energy of binding to the wild type complex, suggesting that the contribution of the short hydrogen bond is not extraordinarily strong.