Pro-sequence of subtilisin can guide the refolding of denatured subtilisin in an intermolecular process

Subtilisin E, an alkaline serine protease consisting of a single polypeptide chain of 275 amino acids is produced from a pre-pro-protein. The pre-sequence functions as the signal peptide for protein secretion across the membrane. Deletion of the pro-sequence yields mature but inactive subtilisin: the 77-amino acid pro-sequence must precede the mature subtilisin to guide the latter into an active conformation. Pro-subtilisin denatured in 6 M guanidine-HCl can be self-processed to the active enzyme intramolecularly, with concomitant cleavage of the pro-sequence, when dialysed against renaturing buffer. We have constructed an active-centre mutant of pro-subtilisin (Asp 32----Asn) which is not processed to active enzyme, unlike the wild-type pro-subtilisin, because intramolecular processing is prevented. Here we report an intermolecular pathway for the refolding of the inactive mature protein to an active enzyme in vitro with the aid of exogenously added pro-sequence. We establish conditions under which the mature inactive form, as well as acid-denatured subtilisins Carlsberg and BPN', can be renatured by the mutant pro-subtilisin.     

Single injections of triazolam,a short-acting benzodiazepine,lengthen the period of the circadian activity rhythm in golden hamsters

Single injections of the benzodiazepine, triazolam, induce phase shifts and cause a lengthening of the circadian activity rhythm in the golden hamster. The effect of triazolam on period depends on the phase of injection, but is not dependent on the direction of the phase shifts. Triazolam injections caused increases in period that were associated with phase advances as well as phase delays in the activity rhythm. This relationship between triazolam-induced phase shifts and changes in period is different from the relationship between light-induced phase shifts and period changes.     

L'énergie atomique

Sans résumé     

Immunological activity of covalently linked T-cell epitopes.

Immune responses to proteins necessarily involve the recognition by T lymphocytes of a peptide or peptides derived from a protein complexed with a major histocompatibility antigen. The T-cell response of BALB/c mice to the bacteriophage lambda cI repressor protein (residues 1-102) is directed predominantly towards the epitope contained within a single peptide encompassing residues 12-26. Similar phenomena of immunodominance of a particular peptide have also been observed in other protein systems. The mechanisms that have been suggested to account for the focusing of the T-cell response are partial deletion in the T-cell repertoire, biased antigen processing, and competition for binding to the presenting molecule, the major histocompatibility complex encoded class II transplantation antigen. In a model system with a polypeptide containing two synthetically linked immunologically active epitopes, we now demonstrate the existence of a hierarchy between these epitopes, so that the immune response elicited is directed mainly towards the more immunogenic epitope, whereas the less immunogenic epitope elicits little or no T-cell reactivity. In addition, the same hierarchy of dominance is also apparent when the polypeptide is used to induce tolerance in the periphery in adult mice. The chimaeric peptide can induce tolerance only towards the more immunogenic epitope. These experiments indicate that the rules governing antigen processing and presentation that result in T-cell activation are apparently the same as the rules that govern the processes resulting in the induction of tolerance.     

Deficiency of kallikrein-like enzyme activities in cerebral tissue of patients with alzheimer's disease

Summary We examined the changes in the intracerebral activities, at the time of postmortem autopsy, in patients with Alzheimer's disease. When compared with the control group, the activity of kallikrein-like enzyme was significantly decreased, while prolyl endopeptidase activity increased, in the patients group. Aprotinin inhibited 50% of the activity of the former enzyme at 2×10^–7M. Taken together with the results of a multivariate study, the above findings may indicate that intracerebral kallikrein deficiency plays an important role in the pathogenesis of Alzheimer's disease.