Crystal structure of the C-terminal three-helix bundle subdomain of C. elegans Hsp70

Hsp70 chaperones are composed of two domains; the 40 kDa N-terminal nucleotide-binding domain (NDB) and the 30 kDa C-terminal substrate-binding domain (SBD). Structures of the SBD from Escherichia coli homologues DnaK and HscA show it can be further divided into an 18 kDa beta-sandwich subdomain, which forms the hydrophobic binding pocket, and a 10 kDa C-terminal three-helix bundle that forms a lid over the binding pocket. Across prokaryotes and eukaryotes, the NBD and beta-sandwich subdomain are well conserved in both sequence and structure. The C-terminal subdomain is, however, more evolutionary variable and the only eukaryotic structure from rat Hsc70 revealed a diverged helix-loop-helix fold. We have solved the crystal structure of the C-terminal 10 kDa subdomain from Caenorhabditis elegans Hsp70 which forms a helical-bundle similar to the prokaryotic homologues. This provides the first confirmation of the structural conservation of this subdomain in eukaryotes. Comparison with the rat structure reveals a domain-swap dimerisation mechanism; however, the C. elegans subdomain exists exclusively as a monomer in solution in agreement with the hypothesis that regions out with the C-terminal subdomain are necessary for Hsp70 self-association.     

Thermal denaturation of soluble calf-skin collagen

1. Soluble calf-skin collagen has been denatured thermally between 37° and 60° and the component proteins have been separated on carboxymethylcellulose. 2. Four main fractions have been separated; α and β (in the nomenclature in common usage) and two other fractions. (The α and β components are complex owing to the presence of α₁, α₂, β₁ and β₂ parts). 3. Fractions 3 and 4 undergo rapid denaturation between 39° and 40° whereafter fraction 4 remains virtually unchanged even at 60°. 4. That portion of fraction 4 which remains at 60° is thought to be identical with the fraction designated γ by other workers, this fraction being composed of three α-chains in covalent linkage (such bonds are alkali-labile). 5. The equilibrium between α, β and fractions 3 and 4 is apparently reversible since acid-soluble collagen after denaturation at 45° or 60° followed by cooling to 0° for 30min. was found to contain only fraction 4 when chromatographed at 37°.     

The effects of clinical practice guidelines on patient outcomes in primary care: a systematic review

OBJECTIVE: To assess the evidence for the effectiveness of clinical practice guidelines (CPGs) in improving patient outcomes in primary care. DATA SOURCES: A search of the MEDLINE, HEALTHPLAN, CINAHL and FAMLI databases was conducted to identify studies published between Jan. 1, 1980, and Dec. 31, 1995, concerning the use of guidelines in primary medical care. The keywords used in the search were "clinical guidelines," "primary care," "clinical care," "intervention," "randomized controlled trial" and "effectiveness." STUDY SELECTION: Studies of the use of CPGs were selected if they involved a randomized experimental or quasi-experimental method, concerned primary care, were related to clinical care and examined patient outcomes. Of 91 trials of CPGs identified through the search, 13 met the criteria for inclusion in the critical appraisal. DATA EXTRACTION: The following data were extracted, when possible, from the 13 trials: country and setting, number of physicians, number of patients (and the proportion followed to completion), length of follow-up, study method (including random assignment method), type of intervention, medical condition treated and effect on patient outcomes (including clinical and statistical significance, with confidence intervals). DATA SYNTHESIS: The most common conditions studied were hypertension (7 studies), asthma (2 studies) and cigarette smoking (2 studies). Four of the studies followed nationally developed guidelines, and 9 used locally developed guidelines. Six studies involved computerized or automated reminder systems, whereas the others relied on small-group workshops and education sessions. Only 5 of the 13 trials (38%) produced statistically significant results. CONCLUSION: There is very little evidence that the use of CPGs improves patient outcomes in primary medical care, but most studies published to date have used older guidelines and methods, which may have been insensitive to small changes in outcomes. Research is needed to determine whether the newer, evidence-based CPGs have an effect on patient outcomes.     

Rearrangement of Genes Located on Homologous Chromosomal Segments in Mouse and Man: The Location of Genes for Alpha-and Beta-Interferon, Alpha-1 Acid Glycoprotein-1 and -2, and Aminolevulinate Dehydratase on Mouse Chromosome 4

Gene mapping studies to determine the order of alpha- and beta-interferon (Ifa, Ifb), aminolevulinate dehydratase (Lv), and alpha-1 acid glycoprotein-1 and -2 (Orm-1, Orm-2) relative to each other and to the reference genes brown (b), B-cell maturation factor responsiveness (Bmfr-1), and major urinary protein-1 (Mup-1) are reported. The most likely order was Mup-1--Lv--b--Orm-1, Orm-2--Ifa, Ifb--Bmfr-1. This order suggested that two chromosomal segments located on chromosome 4 in the mouse and chromosome 9 in man have been conserved since divergence of lineages leading to man and mouse; these segments are marked by soluble aconitase-1 (Aco-1) and galactose-1 phosphate uridyl transferase (Galt) and by Lv and Orm-1. This order also demonstrated that, although genes located on opposite arms of chromosome 9 in man remain syntenic in the mouse, gene order has not been conserved; Ifa and Ifb are not located in their expected locations near Aco-1 and Galt. The position of Ifa and Ifb between Orm-1 and Bmfr-1 could not be determined with certainty because of apparent heterogeneity in recombination frequencies between crosses involving conventional laboratory strains of mice and crosses involving interspecific matings between laboratory mice and Mus spretus. This result suggests that caution must be exercised when using M. spretus in linkage crosses.     

Modification of proteins and other biological molecules by acetaldehyde: adduct structure and functional significance.

1. Chronic ethanol consumption is a major cause of liver disease. The modification of hepatic proteins by acetaldehyde (AcH), the primary metabolite of ethanol, has for some time been suggested as one of the major events initiating alcoholic liver disease. 2. These alterations in protein structure are believed to affect liver cell function, and may serve to activate the immune system. 3. This review considers the interaction between AcH and macromolecules and its functional implications.