Structure of porcine heart cytoplasmic malate dehydrogenase: combining X-ray diffraction and chemical sequence data in structural studies

The amino acid sequence of cytoplasmic malate dehydrogenase (sMDH) has been determined by a combination of X-ray crystallographic and chemical sequencing methods. The initial molecular model incorporated an "X-ray amino acid sequence" that was derived primarily from an evaluation of a multiple isomorphous replacement phased electron density map calculated at 2.5-A resolution. Following restrained least-squares crystallographic refinement, difference electron density maps were calculated from model phases, and attempts were made to upgrade the X-ray amino acid sequence. The method used to find the positions of peptides in the X-ray structure was similar to those used for studying protein homology and was shown to be successful for large fragments. For sMDH, X-ray methods by themselves were insufficient to derive a complete amino acid sequence, even with partial chemical sequence data. However, for this relatively large molecule at medium resolution, the electron density maps were of considerable help in determining the linear position of peptide fragments. The N-acetylated polypeptide chain of sMDH has 331 amino acids and has been crystallographically refined to an R factor of 19% for 2.5-A resolution diffraction data.     

Amino acid sequence of guinea pig prostate kallikrein

The primary structure of the major arginine esteropeptidase from guinea pig prostate has been deduced from automated Edman degradation of peptides generated by clostripain, cyanogen bromide, endoproteinase Lys-C, and Staphylococcus aureus V8 protease digestion of the protein. The esteropeptidase is a single polypeptide chain comprised of 239 amino acids and contains 2 apparent sites of carbohydrate attachment, Asn-78 and Asn-169. Both occur in consensus sequences for N-linked glycosylation sites. The esteropeptidase exhibits approximately 35% homology with trypsin including conservation of the catalytic residues and the aspartic acid which confers specificity toward basic amino acids. The sequence identity, however, extends to greater than 60% with the kallikrein family of serine proteases. In addition to the overall homology, the guinea pig enzyme displays a number of features characteristic of kallikreins including 10 conserved half-cystine residues, a C-terminal proline, and the "kallikrein loop". On the basis of this structural relatedness, the enzyme has been designed as guinea pig prostate kallikrein. In contrast to many of the kallikreins of other species and tissues, this enzyme does not contain any sites within the kallikrein loop sensitive to proteases that result in internal breaks in the polypeptide chain.     

Production of Vero cytotoxin by strains of Escherichia coli as related to the availability of iron

Abstract Vero cytotoxin (VT) producing strains of Escherichia coli (VTEC), including isolates from cases of haemolytic uraemic syndrome and infantile diarrhoea, were used to determine the effect of iron availability on the production of intra- and extracellular VT, with particular interest in elevating toxin production by low-level toxin producing VTEC. Culturing bacteria under iron restriction resulted in growth retardation and a decrease in the production of VT. For the routine detection of both high- and low-level VT-producing E. coli , there was no advantage to be gained by growing bacteria under iron restriction or using disrupted bacterial cell preparations; on the contrary, testing culture supernatants from bacteria grown in iron-replete media for approximately 14 h proved to be the most sensitive and accurate method for detecting VT and the resultant identification of VTEC.     

Pain, paradox, and value

The author argues that "as soon as one begins to study the understanding and management of pain in science, human medicine, and veterinary medicine, one begins to encounter a variety of apparent paradoxes." He contends that these paradoxes, ten of which he identifies and discusses in this essay, are based on flawed philosophical and valuational assumptions underlying science and medicine. Rollins concludes that, as social morality increasingly has an impact on science, a new ideology will evolve that is more receptive to the moral universe and more capable of a "coherent vision of pain, one which acknowledges that the medical notion of adequacy of anaesthesia is as much a moral as a scientific one."     

Detection and partial purification of two lipases fromCandida rugosa

Summary Two distinct lipases produced byCanadida rugosa were identified and separated by a high resolution anion-exchange column (Mono Q) after an ethanol extraction of the crude lipase. From this Mono Q column, lipase I eluted at 0.05 M NaCl whereas lipase II eluted at 0.15 M NaCl. The less anionic nature of lipase I was also confirmed by native polyacrylamide gel electrophoresis as well as isoelectrophoresis. Both proteins have an apparent molecular weight of 58,000 by SDS-PAGE. The isoelectric points of lipase I and II are 5.6 and 5.8 respectively.     

Single-stranded circular DNA generated from broad host range plasmid R1162 and its derivatives

Extraction of R1162 plasmid DNA with the alkaline lysis method yields considerable amounts of single-stranded circular plasmid DNA. Destabilization of plasmid DNA is stimulated by the R1162 mob region in cis. The formation of single-stranded circular DNA is initiated at a specific site on the plasmid, presumably the origin of transfer (oriT).     

Nematode parasites of birds of the fauna in Tunisia

330 birds of Tunisia were necropsied; they belong to 73 species among 29 families and 13 orders. We so collect 36 species of nematodes from 9 families. The relative importance of these is variable. The best represented are: Capillariidae (6 species), Spiruridae (6 species), Acuariidae (9 species) and Filariidae (6 species). The parasitism by nematodes is not uniform. Among the 330 birds autopsied only 51 were parasited by nematodes (15.45%) among 25 of the examined birds species (34.2%). Among these 25, sixteen (64%) presented only one species of parasitic nematode, six (24%) arboured two, (8%) three and only one, (partridges) presents six species of nematodes.     

Oligosaccharide synthesis by enzymatic transglycosylation

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