Structure: Function of Transmembrane Appendages in Gram-Negative Bacteria
Gram-negative bacteria possess diverse transmembrane appendages that allow them to colonize different ecological niches. An essential prokaryotic strategy used for adaptation to various environments is the secretion of several molecules such as proteins and DNA, which is accomplished by specialized secretion systems that enable substrate transport across the cell envelope. Moreover, bacterial motility and adherence, driven by filamentous surface structures as flagella, pili, and curli, also play a crucial role in bacterial colonization. The construction of these macromolecular complexes faces a physical barrier since they must traverse two distinct lipid membrane bilayers and a peptidoglycan cell wall. Therefore, proteins that display special physicochemical characteristics to assemble within the hydrophobic lipid environment serve as building blocks for the biogenesis of the different transmembrane appendages. Here, we review the architecture and function of the main appendages of diderm bacteria and discuss how the interplay between membrane lipids and proteins influences their assembly and activity.
Work in our laboratory is supported by grants from Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México (DGAPA, UNAM; PAPIIT IN209617) and Consejo Nacional de Ciencia y Tecnología (CONACyT 284081). We acknowledge Dra. Norma Espinosa Sánchez for critical reading of the manuscript and excellent technical assistance.
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