Sequence comparison of the EcoHK31I and EaeI restriction-modification systems suggests an intergenic transfer of genetic material

The genes coding for the EcoHK31I and EaeI restriction-modification (R-M) systems from Escherichia coli strain HK31 and Enterobacter aerogenes, respectively, have been cloned and sequenced. Both ENases recognize and cleave Y/GGCCR leaving 4 nucleotide 5'-protruding ends, while the MTases modify the internal cytosine. The systems were isolated on a 2.3kb AseI fragment for EcoHK31I, and a 4.6 kb HindIII fragment for EaeI. The R and M genes of both systems converge and overlap by 14 nucleotides. Previously, we found that M.EcoHK31I consisted of two subunits, (alpha and beta), with the beta subunit being translated from an alternative open reading frame within the gene encoding the alpha subunit. Sequence comparison between the EcoHK31I and EaeI systems reveals striking similarity. The eaeIM gene also encodes alpha and beta polypeptides of 309 and 176 amino acids which share 96% and 97% identity, respectively, with those of ecoHK31IM. ecoHK31IR and eaeIR encode proteins of 318 and 315 aa, respectively, which share 92% identity but are otherwise unique in the GenBank database. The EaeI and the EcoHK31I R-M systems were found to be flanked by genes coding for integrases. It is possible that these integrases have facilitated the transfer of this system among different bacterial species.     

Crystal structure of restriction endonuclease BglI bound to its interrupted DNA recognition sequence

The crystal structure of the type II restriction endonuclease BglI bound to DNA containing its specific recognition sequence has been determined at 2.2 A resolution. This is the first structure of a restriction endonuclease that recognizes and cleaves an interrupted DNA sequence, producing 3' overhanging ends. BglI is a homodimer that binds its specific DNA sequence with the minor groove facing the protein. Parts of the enzyme reach into both the major and minor grooves to contact the edges of the bases within the recognition half-sites. The arrangement of active site residues is strikingly similar to other restriction endonucleases, but the co-ordination of two calcium ions at the active site gives new insight into the catalytic mechanism. Surprisingly, the core of a BglI subunit displays a striking similarity to subunits of EcoRV and PvuII, but the dimer structure is dramatically different. The BglI-DNA complex demonstrates, for the first time, that a conserved subunit fold can dimerize in more than one way, resulting in different DNA cleavage patterns.     

A multiperspective, multivariable evaluation of reliable change

N. S. Jacobson and P. Truax's (1991) method for evaluating the clinical significance of client change has gained some prominence in psychotherapy outcome research. However, little has been done to investigate the validity of this methodology. This study addresses this limitation by comparing (a) the perceived level of change (as subjectively reported from 3 distinct perspectives) across outcome groupings based on Jacobson and Truax's reliable change index (RCI) and (b) subjective reports of therapeutic alliance and satisfaction across outcome groupings. The results of these comparisons indicate that the RCI is effective in identifying those who make reliable improvement in therapy but is less effective in differentiating between no-changers and deteriorators. In addition, the relationship between treatment outcome and satisfaction with service is questioned.     

A multiperspective comparison of satisfaction, symptomatic change, perceived change, and end-point functioning.

Measures of satisfaction have become increasingly popular as indications of psychotherapy outcome both in research and in practice. Several studies have explored the relationship between satisfaction and symptomatic change, with mixed results. The present study examines the relationship among satisfaction, symptomatic improvement, perceived change, and end-point functioning from multiple perspectives. Sixty-six clients from 2 Midwestern community mental health centers, 48 of their spouses and significant others, and their therapists participated in the study. Results indicated that satisfaction was not significantly related to symptomatic change. Satisfaction and perceived change were significantly related from all 3 perspectives. Satisfaction was also significantly related to end-point functioning from the client and significant other perspectives. The unique contribution of satisfaction data to a comprehensive outcome evaluation strategy is discussed. Researchers, administrators, and practitioners are encouraged to use satisfaction measures with a greater awareness of both their strengths and their limitations as outcome indicators. (PsycINFO Database Record (c) 2010 APA, all rights reserved)