Cytosolic and ER J-domains of mammalian and parasitic origin can functionally interact with DnaK.

Both prokaryotic and eukaryotic cells contain multiple heat shock protein 40 (Hsp40) and heat shock protein 70 (Hsp70) proteins, which cooperate as molecular chaperones to ensure fidelity at all stages of protein biogenesis. The Hsp40 signature domain, the J-domain, is required for binding of an Hsp40 to a partner Hsp70, and may also play a role in the specificity of the association. Through the creation of chimeric Hsp40 proteins by the replacement of the J-domain of a prokaryotic Hsp40 (DnaJ), we have tested the functional equivalence of J-domains from a number of divergent Hsp40s of mammalian and parasitic origin (malarial Pfj1 and Pfj4, trypanosomal Tcj3, human ERj3, ERj5, and Hsj1, and murine ERj1). An in vivo functional assay was used to test the functionality of the chimeric proteins on the basis of their ability to reverse the thermosensitivity of a dnaJ cbpA mutant Escherichia coli strain (OD259). The Hsp40 chimeras containing J-domains originating from soluble (cytosolic or endoplasmic reticulum (ER)-lumenal) Hsp40s were able to reverse the thermosensitivity of E. coli OD259. In all cases, modified derivatives of these chimeric proteins containing an His to Gln substitution in the HPD motif of the J-domain were unable to reverse the thermosensitivity of E. coli OD259. This suggested that these J-domains exerted their in vivo functionality through a specific interaction with E. coli Hsp70, DnaK. Interestingly, a Hsp40 chimera containing the J-domain of ERj1, an integral membrane-bound ER Hsp40, was unable to reverse the thermosensitivity of E. coli OD259, suggesting that this J-domain was unable to functionally interact with DnaK. Substitutions of conserved amino acid residues and motifs were made in all four helices (I-IV) and the loop regions of the J-domains, and the modified chimeric Hsp40s were tested for functionality using the in vivo assay. Substitution of a highly conserved basic residue in helix II of the J-domain was found to disrupt in vivo functionality for all the J-domains tested. We propose that helix II and the HPD motif of the J-domain represent the fundamental elements of a binding surface required for the interaction of Hsp40s with Hsp70s, and that this surface has been conserved in mammalian, parasitic and bacterial systems.

Optimization of catechol production by membrane-immobilized polyphenol oxidase: a modeling approach.

Although previous research has focused on phenol removal efficiencies using polyphenol oxidase in nonimmobilized and immobilized forms, there has been little consideration of the use of polyphenol oxidase in a biotransformation system for the production of catechols. In this study, polyphenol oxidase was successfully immobilized on various synthetic membranes and used to convert phenolic substrates to catechol products. A neural network model was developed and used to model the rates of substrate utilization and catechol production for both nonimmobilized and immobilized polyphenol oxidase. The results indicate that the biotransformation of the phenols to their corresponding catechols was strongly influenced by the immobilization support, resulting in differing yields of catechols. Hydrophilic membranes were found to be the most suitable immobilization supports for catechol production. The successful biocatalytic production of 3-methylcatechol, 4-methylcatechol, catechol, and 4-chlorocatechol is demonstrated.

Prediction of nurses' job satisfaction level.

Indications are that job satisfaction of nurses in South Africa is at a low level. The need to determine factors related to this situation prompted a study in which an attempt was made to determine whether self-concept (measured by Vrey's self-concept Scale) and career orientation scores (determined by means of the Career Orientation Inventory (COI) developed by Schein) could predict the level of job satisfaction of nurses (measured by means of the Minnesota Job Satisfaction Questionnaire (MSQ)). The instruments were applied to 86 professional nurses employed in an academic (teaching) hospital. The sample was divided into a high satisfaction group (N = 46) and a low satisfaction (N = 40) group. Hotelling's T2, MANOVA, Stepwise Multiple Regression and discriminant analyses were used to analyze the data. Results indicated that the two groups differed on several self-concept scales and on one career orientation scale. Eighteen per cent of the variance in job satisfaction could be explained by means of career orientation and self-concept scores. Sixty seven per cent of the respondents were placed in the correct group (in terms of their job satisfaction level) using self-concept and career orientation scores.

Job involvement and job satisfaction of South African nurses compared with other professions.

The study was designed primarily to compare the work outcomes of job satisfaction and job involvement of South African nurses with those of members of 13 other professional groups in South Africa and with American nurses where data was available. Secondary aims included identifying areas where job satisfaction was particularly low and demonstrating the relative independence of the job involvement and job satisfaction constructs. A questionnaire incorporating the Kanungo Job Involvement Scale and the Short Form of the Minnesota Job Satisfaction Questionnaire was mailed to random samples of people between the ages of 29 and 41 drawn from 14 professional registers. There were 114 nurses in the final sample and 1677 members of other professions. Differences among professions were tested for significance using one-way analyses of variance and Bonferroni ranges tests. South African Nurses were shown to have extremely low job satisfaction relative to American nurses and to other professional groups in South-Africa. By contrast their job involvement was moderately high. The implications of these findings for the medical profession as a whole and for nurses in particular are discussed. The fear is expressed that wide spread dissatisfaction may lead to fewer people entering the profession and highly trained people leaving.