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Membrane Anchoring (membrane + anchoring)
Selected AbstractsExpression of PRiMA in the mouse brain: membrane anchoring and accumulation of ,tailed' acetylcholinesteraseEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2003Noël A. Perrier Abstract We analysed the expression of PRiMA (proline-rich membrane anchor), the membrane anchor of acetylcholinesterase (AChE), by in situ hybridization in the mouse brain. We compared the pattern of PRiMA transcripts with that of AChE transcripts, as well as those of choline acetyltransferase and M1 muscarinic receptors which are considered pre- and postsynaptic cholinergic markers. We also analysed cholinesterase activity and its molecular forms in several brain structures. The results suggest that PRiMA expression is predominantly or exclusively related to the cholinergic system and that anchoring of cholinesterases to cell membranes by PRiMA represents a limiting factor for production of the AChE tailed splice variant (AChET),PRiMA complex, which represents the major AChE component in the brain. This enzyme species is mostly associated with cholinergic neurons because the pattern of PRiMA mRNA expression largely coincides with that of ChAT. We also show that, in both mouse and human, PRiMA proteins exist as two alternative splice variants which differ in their cytoplasmic regions. [source] Flk prevents premature secretion of the anti-, factor FlgM into the periplasmMOLECULAR MICROBIOLOGY, Issue 3 2006Phillip Aldridge Summary The flk locus of Salmonella typhimurium was identified as a regulator of flagellar gene expression in strains defective in P- and l -ring formation. Flk acts as a regulator of flagellar gene expression by modulating the protein levels of the anti-,28 factor FlgM. Evidence is presented which suggests that Flk is a cytoplasmic-facing protein anchored to the inner membrane by a single, C-terminal transmembrane-spanning domain (TMS). The specific amino acid sequence of the TMS is not essential for Flk activity, but membrane anchoring is essential. Membrane fractionation and visualization of protein fusions of green fluorescent protein derivatives to Flk suggested that the Flk protein is present in the membrane as punctate spots in number that are much greater than the number of flagellar basal structures. The turnover of the anti-,28 factor FlgM was increased in flk mutant strains. Using FlgM,,-lactamase fusions we show the increased turnover of FlgM in flk null mutations is due to FlgM secretion into the periplasm where it is degraded. Our data suggest that Flk inhibits FlgM secretion by acting as a braking system for the flagellar-associated type III secretion system. A model is presented to explain a role for Flk in flagellar assembly and gene regulatory processes. [source] Topological analysis and role of the transmembrane domain in polar targeting of PilS, a Pseudomonas aeruginosa sensor kinaseMOLECULAR MICROBIOLOGY, Issue 4 2000Julie Ethier In Pseudomonas aeruginosa, synthesis of pilin, the major protein subunit of the pili, is regulated by a two-component signal transduction system in which PilS is the sensor kinase. PilS is an inner membrane protein found at the poles of the bacterial cell. It is composed of three domains: an N-terminal hydrophobic domain; a central cytoplasmic linker region; and the C-terminal transmitter region conserved among other sensor kinases. The signal that activates PilS and, consequently, pilin transcription remains unknown. The membrane topology of the hydrophobic domain was determined using the lacZ and phoA gene fusion approach. In this report, we describe a topological model for PilS in which the hydrophobic domain forms six transmembrane helices, whereas the N- and C-termini are cytoplasmic. This topology is very stable, and the cytoplasmic C-terminus cannot cross the inner membrane. We also show that two of the six transmembrane segments are sufficient for membrane anchoring and polar localization of PilS. [source] Role of prolipoprotein diacylglyceryl transferase (Lgt) and lipoprotein-specific signal peptidase II (LspA) in localization and physiological function of lipoprotein MsmE in Streptococcus mutansMOLECULAR ORAL MICROBIOLOGY, Issue 6 2008T. Arimoto Introduction:, To clarify the role that prolipoprotein diacylglyceryl transferase (Lgt) and lipoprotein-specific signal peptidase II (LspA) play in the physiological function of MsmE, we constructed lgt -deficient and lspA -deficient mutants of Streptococcus mutans 109c and examined the potential role of Lgt and LspA in membrane anchoring and growth in a melibiose medium of S. mutans. Methods:, The lgt -, lspA -, and msmE -deficient mutants of S. mutans 109c were constructed by double-crossover recombination of their respective genes. Localization of MsmE was demonstrated by Western blot analysis with an MsmE antiserum. The growth of S. mutans cells was examined in a Trypton medium containing melibiose or glucose. Results:, In the S. mutans lgt mutant, localization of the surface lipoprotein MsmE changed with the culture supernatant. The growth of the S. mutans lgt and lspA mutants was remarkably reduced in the melibiose medium; however, growth was recovered in the strains complemented with the lgt or the lspA gene. Therefore, lipid-modification by Lgt and subsequent signal peptide cleavage by LspA were crucial for membrane anchoring and the physiological function of MsmE in S. mutans. Conclusion:, These results demonstrate that MsmE is required for melibiose metabolism in S. mutans and that modification by Lgt and LspA are important processes for the physiological function of MsmE. [source] | ||||||||||