The amino-terminal domain of human signal transducers and activators of transcription 1: overexpression, purification and characterization.

The dual functional signal transducers and activators of transcription (STAT) proteins are latent cytoplasmic transcription factors that play crucial roles in host defense. Animals that lack these proteins are highly susceptible to microbial and viral infections and chemically induced primary tumours. We have over expressed the amino-terminal domain of human STAT1 (hSTAT1) in Escherichia coli and purified it by affinity chromatography and gel filtration chromatography. The entire process has been monitored by gel electrophoresis. The pure protein has been characterized by mass spectrometry and 2-dimensional nuclear magnetic resonance (2D-NMR) spectroscopy. Our results indicate that the N-terminus of hSTAT1 exists as a dimer in solution.

Conformation of the C-terminal pentapeptide—the ‘message sequence’—of tachykinins as determined by consensus dynamic.

The tachykinins are a family of gastrointestinal peptides comprising eight members: substance P, neurokinin A, neurokinin Β, eledoisin, physalemin, uperolein, kassinin and phyllomedusin. Consensus dynamics was carried out on an ensemble of seven tachykinins to determine the binding conformation of the common C-terminal fragment: Phe-X-Gly-Leu-Met-NH2, the ‘message sequence’ of tachykinins. Three binding modes for the C-terminal pentapeptide were determined. The first binding conformation is folded due to an intramolecular Η-bond between the NH of the variable residue (X) and CO of Met. Other features include γ-bends at both the variable amino acid (X) and at Gly. The global minimum of the simulation has this conformation for the C-terminal pentapeptide. The other two binding modes have slightly higher energies. The second is chiefly characterized by a β-turn around the segment X-Gly-Leu-Met, with additional γ-bends at the variable amino acid (X) and Met. The final binding conformation is composed of γ-bends around the variable amino acid (X) and Leu, and a ‘pseudo’ γ-bend at the terminal Met.

Pharmacophores of the dual acting α, β-blockers as deduced, from molecular dynamics simulations.

The dual acting α, β-blockers have an important place in the management of hypertension. Molecular dynamics simulations have been carried out on all stereoisomers of seven dual acting α,β-blockers namely adimolol, amosulalol, bucindolol, carvedilol, labetalol, medroxalol and primidolol. Three families of conformations have been identified for the group of compounds. The pharmacophores for α and β-activity have been constructed for two of these families.