Optimised fermentation strategy for 13C/15N recombinant protein labelling in Escherichia coli for NMR-structure analysis.

A widely applicable cultivation strategy, which reduces the costs of expensive isotopes, is designed for maximal (98-100%) incorporation of [13C] and [15N] into labelled recombinant protein expressed in Escherichia coli, allowing better assignment of the resonances for NMR studies. Isotope labelling of the culture was performed throughout the complete process, starting from preculture. Sufficient biomass is first generated in a batch phase. Upon consumption of glucose, identified by a sharp drop of on-line monitored oxygen consumption, expression is induced and cultivation is continued under glucose-limited conditions as fed-batch process. Thereby a quantitative utilisation of the most expensive component [13C]-glucose is achieved, while the approximate amount of the [15N]-ammonium chloride to be incorporated is calculated from the scheduled biomass. The usefulness of the strategy is demonstrated with production of uniformly [13C/15N]-labelled tryparedoxin of Crithidia fasciculata. Ideal isotope incorporation and product quality is documented by MALDI-TOF mass spectrometry and two- and three-dimensional NMR spectra.

Hydroxamate derivatives of substrate-analogous peptides containing aminomalonic acid are potent inhibitors of matrix metalloproteinases.

Novel peptides containing the sequence -Pro-Leu-Ama(NHOH)- were synthesized and characterized by spectroscopic techniques. Their inhibitory properties towards the activated form of native human gelatinase B (MMP-9) and the catalytic domain of neutrophil collagenase (cdMMP-8) were determined. The most effective inhibitor synthesized exhibits Ki values of 2 x 10(-6) M (cdMMP-8) and 5 x 10(-9) M (MMP-9) thus attaining interesting discrimination between the tested metalloproteinases. A most important feature of this type of inhibitor is its peptide nature making the compounds similar to natural substrates. In spite of the peptide character of the inhibitors synthesized, the P1-P1'-peptide bond shows a high resistance to cleavage by the proteinases.