Mitochondrial Lysyl-tRNA Synthetase Independent Import of tRNA Lysine into Yeast Mitochondria

Aminoacyl tRNA synthetases play a central role in protein synthesis by charging tRNAs with amino acids. Yeast mitochondrial lysyl tRNA synthetase (Msk1), in addition to the aminoacylation of mitochondrial tRNA, also functions as a chaperone to facilitate the import of cytosolic lysyl tRNA. In this report, we show that human mitochondrial Kars (lysyl tRNA synthetase) can complement the growth defect associated with the loss of yeast Msk1 and can additionally facilitate the in vitro import of tRNA into mitochondria. Surprisingly, the import of lysyl tRNA can occur independent of Msk1 in vivo. This suggests that an alternative mechanism is present for the import of lysyl tRNA in yeast

Functions Of Cytochrome-C In Regulation Of Electron-Transfer And Protein Folding

Cytochrome c, a "mobile electron carrier" of the mitochondrial respiratory chain, also occurs in detectable amounts in the cytosol, and can receive electrons from cytochromes present in endoplasmic reticulum and plasma membranes as well as from superoxide and ascorbate. The pigment was found to dissociate from mitochondrial membranes in liver and kidney when rats were subjected to heat exposure and starvation, respectively. Treating cytochrome c with hydroxylamine gives a partially deaminated product with altered redox properties; decreased stimulation of respiration by deficient mitochondria, increased reduction by superoxide, and complete loss of reducibility by plasma membranes. Mitochondria isolated from brown adipose tissue of cold-exposed rats are found to be sub-saturated with cytochrome c. The ability of cytochrome c to reactivate reduced ribonuclease is now reinterpreted as a molecular chaperone role for the hemoprotein

Collaborative organizational forms: on communities, crowds, and new hybrids

Abstract In this article, I examine collaborative organizational forms in terms of their institutional properties and the mechanisms by which they solve the universal problems of organizing. Based on three ideal forms—markets, hierarchies, and communities—I propose a framework for analyzing and mapping organizational forms. The framework expands our understanding of the ideal forms and derives a set of analytically distinct hybrids at the intersection of the ideal types. The framework also specifies the main conditions that drive organizations to change form and move toward another hybrid or ideal form. The theoretical review of collaborative organizational forms is illustrated and informed by three empirical cases of new forms within the domains of drug discovery, software development, as well as professional services. Further, I discuss plural forms and the role of hierarchy in collaborative forms. Finally, I outline implications for research and practice in terms of comparative analysis of organizational forms, the role of crowds, as well as the interplay between new technologies and new organizational forms