Zusammenfassung
Solenoid proteins, which are distinguished from general globular proteins by their modular architectures, are frequently involved in signal transduction pathways. Proteins from the tetratricopeptide repeat (TPR) and Sell-like repeat (SLR) families share similar alpha-helical conformations but different consensus sequence lengths and superhelical topologies. Both families are characterized by low ...
Zusammenfassung
Solenoid proteins, which are distinguished from general globular proteins by their modular architectures, are frequently involved in signal transduction pathways. Proteins from the tetratricopeptide repeat (TPR) and Sell-like repeat (SLR) families share similar alpha-helical conformations but different consensus sequence lengths and superhelical topologies. Both families are characterized by low sequence similarity levels, rendering the identification of functional homologous difficult. Therefore current knowledge of the molecular and cellular functions of the SLR proteins Sell, Hrd3, Chs4, Nif1, PodJ, ExoR, AlgK, HcpA, Hsp12, EnhC, LpnE, MotX, and MerG has been reviewed. Although SLR proteins possess different cellular functions they all seem to serve as adaptor proteins for the assembly of macromolecular complexes. Sell, Hrd3, Hspl2 and LpnE are activated under cellular stress. The eukaryotic Sell and Hrd3 proteins are involved in the ER-associated protein degradation, whereas the bacterial LpnE, EnhC, HcpA, ExoR, and AlgK proteins mediate the interactions between bacterial and eukaryotic host cells. LpnE and EnhC are responsible for the entry of L. pneumophila into epithelial cells and macrophages. ExoR from the symbiotic microorganism S. melioti and AlgK from the pathogen P. aeruginosa regulate exopolysaccaride synthesis. Nifl and Chs4 from yeast are responsible for the regulation of mitosis and septum formation during cell division, respectively, and PodJ guides the cellular differentiation during the cell cycle of the bacterium C. crescentus. Taken together the SLR motif establishes a link between signal transduction pathways from eukaryotes and bacteria. The SLR motif is so far absent from archaea. Therefore the SLR could have developed in the last common ancestor between eukaryotes and bacteria. (c) 2006 Elsevier Inc. All rights reserved.
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