Progress in the development of integrated advanced ST plasma scenarios in NSTX (Ono et al 2000 Nucl. Fusion 40 557) is reported. Recent high-performance plasmas in NSTX following lithium coating of the plasma facing surfaces have achieved higher elongation and lower internal inductance than previously. Analysis of the thermal confinement in these lithiumized discharges shows a stronger plasma current and weaker toroidal field dependence than in previous ST confinement scaling studies; the ITER-98(y, 2) scaling expression describes these scenarios reasonably well. Analysis during periods free of MHD activity has shown that the reconstructed current profile can be understood as the sum of pressure driven, inductive and neutral beam driven currents, without requiring any anomalous fast-ion transport. Non-inductive fractions of 65–70%, and βP > 2, have been achieved at lower plasma current. Some of these low-inductance discharges have a significantly reduced no-wall βN limit, and often have βN at or near the with-wall limit. Coupled m/n = 1/1 + 2/1 kink/tearing modes can limit the sustained β values when rapidly growing ideal modes are avoided. A βN controller has been commissioned and utilized in sustaining high-performance plasmas. ‘Snowflake’ divertors compatible with high-performance plasmas have been developed. Scenarios with significantly larger aspect ratios have also been developed, in support of next-step ST devices. Overall, these NSTX plasmas have many characteristics required for next-step ST devices.

Investigation of the chromosomal region downstream of the lacZ gene from Lactobacillus delbrueckii subsp. bulgaricus revealed the presence of a gene (prtB) encoding a proteinase of 1,946 residues with a predicted molecular mass of 212 kDa. The deduced amino acid sequence showed that PrtB proteinase displays significant homology with the N termini and catalytic domains of lactococcal PrtP cell surface proteinases and is probably synthesized as a preproprotein. However, the presence of a cysteine near the histidine of the PrtB active site suggests that PrtB belongs to the subfamily of cysteine subtilisins. The C-terminal region strongly differs from those of PrtP proteinases by having a high lysine content, an imperfect duplication of 41 residues, and a degenerated sequence compared with the consensus sequence for proteins anchoring in the cell walls of gram-positive bacteria. Finally, the product of the truncated prtM-like gene located immediately upstream of the prtB gene seems too short to be involved in the maturation of PrtB.Lactobacillus delbrueckii subsp. bulgaricus is one of the lactic acid bacteria used in industrial milk fermentation. The proteolytic system is essential to ensure rapid growth in milk and supply auxotrophic lactic acid bacteria with amino acids from caseins, the major milk proteins. This system is complex and has been extensively studied in lactococci (21, 35). The first step in milk casein degradation is performed by a cell surface proteinase, PrtP. Two types of PrtP enzymes have been distinguished on the basis of their substrate specificities. PI-type proteinases preferentially cleave ␤-casein, whereas PIII-type enzymes degrade ␣, ␤, and caseins (10). Lactococcal PrtPs are serine proteases and show extensive homology with subtilisins secreted by bacilli. Lactococcal proteinases are synthesized as inactive preproproteins. An N-terminal signal peptide of 33 residues is removed during translocation through the cytoplasmic membrane, and the C terminus remains anchored in the cell envelope. Then, a maturation process mediated by a membrane-located lipoprotein, PrtM, leads to the removal of the pro region (154 residues). The 33-kDa PrtM protein is encoded by a gene located immediately upstream and in the opposite direction of prtP (13, 49). Incubation of lactococci cells in a calcium-free buffer promotes self-digestion of the carboxy terminus of PrtP and its release into the extracellular medium.Lactobacilli have been investigated to a lesser extent but display a high cell surface proteinase activity with substrate specificity differing from that of lactococci (4). Cell surface proteinases have been purified from Lactobacillus paracasei subsp. paracasei NCDO151, L. helveticus CNRZ303, and L89, and L. delbrueckii subsp. bulgaricus CNRZ397 (24, 27, 33, 52). The sequence of the gene encoding proteinase from L. paracasei subsp. paracasei was determined; the deduced amino acid sequence shows 1,902 residues and a high degree of identity (96%) with lactococcal PrtP (15). The presence of a prtM gene ...

The proline iminopeptidase (PeplP) of Lactobacillus delbrueckii subsp. bulgaricus is a major peptidase located in the cell envelope. I t s structural gene (peplP) has been cloned into pUC18 and expressed a t a very high level inCellulai;e (CNRS UMR 106), Universite 'Iaude BernardLyon I, Bat. 405, F-69622 Vi I leu rba n ne Cedex, France Escherichia coli t o give a PeplP activity 15000-fold higher than that found in L. delbrueckii subsp. bulgaricus. The nucleotide sequence of the peplP gene revealed an open reading frame of 295 codons encoding a protein with a predicted M, of 33006, which is consistent with the apparent size of the gene product. The amino acid sequence of PeplP shows significant homology with those of other hydrolases involved in the degradation of cyclic compounds. In particular, there i s a region which includes an identified catalytic site containing a serine residue and a motif specific for the active sites of prolyloligopeptidases (Gly-X-Ser-X-Gly-Gly). The PeplP opens a new way for supplying cells with proline using the peptides resulting from the proteolytic degradation of caseins.