Résumé
Differences of protonated and lithiated leucine-enkephalin(LE) were investigated by hydrogen deuterium exchange-mass spectrometry(HDX-MS) combined with quantum chemistry calculation. The results revealed that the protonated ions possessed very high product yield with all hydrogen atoms being exchanged, while the reaction of lithiated LE stopped after exchanging five hydrogen atoms in the same experimental conditions. The different HDX behaviours probably indicated their conformational differences. To further clarify the experimental results, the most stable conformations of protonated and lithiated leucine-enkephalin were calculated by density functional theory. It was found that terminal amino group was the most thermodynamically stable protonation site,while Li+in coordination of four carbonyl oxygen atoms formed the most favourable lithiated LE. The reaction field reduction of lithium LE was probably due to the less acidity of hydrogen atoms and the increasing rigid conformation change induced by lithium ion.
Résumé
Heat shock protein 90 (HSP90) is a member of genetically conserved heat shock protein family. As an important molecular chaperone in eukaryotic cells, HSP90 plays a key regulatory role in maintaining cellular protein homeostasis. HSP90 clients encompass a wide range of proteins, thus HSP90 is involved in diverse biological process. With the deeper study, it is found that HSP90 takes an important part in the development and metastasis of cancer,and has become a promising target for the study of anticancer biology. We review the progress of HSP90 as molecular chaperone and its relationship with cancer.