The 7-methyl guanosine cap structure of RNA is essential for key aspects of RNA processing, including pre-mRNA splicing, 3' end formation, U snRNA transport, nonsense-mediated decay and translation. Two cap-binding proteins mediate these effects: cytosolic eIF-4E and nuclear cap-binding protein complex (CBC). The latter consists of a CBP20 subunit, which binds the cap, and a CBP80 subunit, which ensures high-affinity cap binding. Here we report the 2.1 A resolution structure of human CBC with the cap analog m7GpppG, as well as the structure of unliganded CBC. Comparisons between these structures indicate that the cap induces substantial conformational changes within the N-terminal loop of CBP20, enabling Tyr 20 to join Tyr 43 in pi-pi stacking interactions with the methylated guanosine base. CBP80 stabilizes the movement of the N-terminal loop of CBP20 and locks the CBC into a high affinity cap-binding state. The structure for the CBC bound to m7GpppG highlights interesting similarities and differences between CBC and eIF-4E, and provides insights into the regulatory mechanisms used by growth factors and other extracellular stimuli to influence the cap-binding state of the CBC.

Branching enzyme catalyzes the formation of ␣-1,6 branch points in either glycogen or starch. We report the 2.3-Å crystal structure of glycogen branching enzyme from Escherichia coli. The enzyme consists of three major domains, an NH 2 -terminal seven-stranded ␤-sandwich domain, a COOH-terminal domain, and a central ␣/␤-barrel domain containing the enzyme active site. While the central domain is similar to that of all the other amylase family enzymes, branching enzyme shares the structure of all three domains only with isoamylase. Oligosaccharide binding was modeled for branching enzyme using the enzyme-oligosaccharide complex structures of various ␣-amylases and cyclodextrin glucanotransferase and residues were implicated in oligosaccharide binding. While most of the oligosaccharides modeled well in the branching enzyme structure, an approximate 50°rotation between two of the glucose units was required to avoid steric clashes with Trp 298 of branching enzyme. A similar rotation was observed in the mammalian ␣-amylase structure caused by an equivalent tryptophan residue in this structure. It appears that there are two binding modes for oligosaccharides in these structures depending on the identity and location of this aromatic residue.

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2-Keto-3-deoxy-6-phosphogluconate (KDPG) aldolase from Pseudomonas putida is a key enzyme in the Entner-Doudoroff pathway which catalyses the cleavage of KDPG via a class I Schiff-base mechanism. The crystal structure of this enzyme has been refined to a crystallographic residual R = 17.1% (R(free) = 21.4%). The N-terminal helix caps one side of the torus of the (betaalpha)(8)-barrel and the active site is located on the opposite, carboxylic side of the barrel. The Schiff-base-forming Lys145 is coordinated by a sulfate (or phosphate) ion and two solvent water molecules. The interactions that stabilize the trimer are predominantly hydrophobic, with the exception of the cyclically permuted bonds formed between Glu132 OE1 of one molecule and Thr129 OG1 of a symmetry-equivalent molecule. Except for the N-terminal helix, the structure of KDPG aldolase from P. putida closely resembles the structure of the homologous enzyme from Escherichia coli.

Raman spectroscopy was used to design and monitor a lysozyme protein batch crystallization process in a lab scale study to facilitate the design of a pharmaceutical protein manufacturing process. A D-optimal design that consisted of 18 experiments was performed to elucidate the effect of temperature, concentration of the precipitating agent, time of crystallization, and possible interactions between these three factors on the Raman scattering changes. A polynomial mathematical model was calculated relating the scattering of the lysozyme solutions measured at individual Raman shifts to the significant factors obtained in the previous crystallization experiment. The 2,940-cm −1 band provided the highest correlation values indicative of small prediction errors and good predictive ability for the crystallization model. Raman scattering signals obtained during the experiments were used as input to obtain a response surface for the factors studied and elucidate the relationship between the crystallization process conditions and the crystals obtained. The main factors affecting the crystallization process were the sodium chloride concentration and temperature.

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