ABSTRACT
Isoprene synthase (ISPS) catalyzes the elimination of pyrophosphate from dimethylallyl diphosphate (DMADP) forming isoprene, a volatile hydrocarbon emitted from many plant species to the atmosphere. In the present work, immunological techniques were applied to study and localize ISPS in poplar leaves (Populus x canescens). Immunogold labeling using polyclonal antibodies generated against His-tagged recombinant ISPS protein detected ca. 44% of ISPS in the stroma of the chloroplasts and ca. 56% of gold particles attached to the stromal-facing side of the thylakoid membranes. ISPS isolated from leaves exhibited the same biochemical properties as the recombinant ISPS without the plastid-targeting peptide heterologous expressed in E. coli, whereas an additional C- or N-terminal His-tag changed the biochemical features of the recombinant enzyme with regard to temperature, pH, and substrate dependence. In comparison to the closely related class of monoterpene synthases from angiosperms and ISPS of oaks, the most striking feature of the poplar ISPS is a cooperative substrate dependence which is characteristic to enzymes with positive substrate activation. The detection of four immunoreactive bands in poplar leaf extracts with isoelectric points from 5.0 to 5.5 and a native molecular weight of ca. 51 kDa give reason for future studies on post-translational modifications of ISPS.
Subject(s)
Alkyl and Aryl Transferases/chemistry , Populus/enzymology , Alkyl and Aryl Transferases/genetics , Alkyl and Aryl Transferases/isolation & purification , Alkyl and Aryl Transferases/metabolism , Immunochemistry , Kinetics , Populus/genetics , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Substrate Specificity , Tissue DistributionABSTRACT
Self-help groups formed increased since the beginning of the eighties; in the field of health especially chronically ill persons met to cope with their daily illness-related problems. As these self-help-initiatives developed into suppliers of services this study should provide information about the special quality of counselling concepts and other services. A telephone interview with 224 self-help initiatives revealed a high proportion of counselling activity (75%). Based on the concept of Grounded Theory a qualitative analysis shows that the perspectives "service provision" and "social support" examined separately so far can only be understood in their combination. Especially community narratives proved to be connecting structural elements on which counselling concepts are based. These community narratives were reconstructed from narrative patterns of stories, mottos, rituals and others. Further essential structural elements are the principle of mutuality, the collective search for a panacea, processes of empowerment and the reference to everday life and environment. The principle of self-help and empowerment is highly valued by the patients. To incorporate this principle in the health care system a closer cooperation of these two systems should be strived for. Therefore it is necessairy to develop a theory of self-help specific counselling in combination with results from salutogenesis research.