title: Twin arginine translocase pathway and fast-folding lipoprotein biosynthesis in E. coli: interesting implications and applications.
abstract: Bacterial lipoproteins, an important class of membrane proteins, are generally thought to be translocated in an unfolded state by the well-studied Sec machinery, whereas the role of TAT, meant for folded proteins, is hardly investigated. Using appropriately engineered fast-folding Enhanced Green Fluorescence Protein (EGFP), as a model, here we show that TAT is essential for not only translocating fast-folding lipoprotein but also its lipid modification. EGFP was lipid-modified and targeted to the outer membrane's outer surface with a prototypical TAT signal sequence containing lipobox but not with the lipoprotein or TAT signal sequence. Justifiably signal sequences of many substrate-binding and co-factor-containing lipoproteins contained both TAT-box and lipobox (Shruthi et al., submitted). Cytoplasmic accumulation of unmodified precursors of engineered EGFP in a tatC mutant implicated this TAT-box-recognizing component in lipid-modification. Similar observations reported earlier with Sec components and murein lipoprotein led us to propose that the translocation-competent and translocase-associated (Sec or TAT) precursor form is prerequisite to initiation of lipid-modification in vivo. The above missing links between translocation and lipid modification machineries in vivo is important to our understanding of bacterial lipoprotein biosynthesis and its utility as a protein engineering tool for potent applications in synthetic biology and nanobiotechnology like display, arrays on bacterial surfaces, vaccines and biosensors.
authors.affiliation: Centre for Biotechnology, Anna University, Chennai-600025, Tamil Nadu, India. ksankran@yahoo.com
authors.forename: Hamsanathan
authors.initials: H
authors.lastname: Shruthi
authors.forename: Prakash
authors.initials: P
authors.lastname: Anand
authors.forename: Vadivel
authors.initials: V
authors.lastname: Murugan
authors.forename: Krishnan
authors.initials: K
authors.lastname: Sankaran
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D001120:Arginine / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D049452:Green Fluorescent Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D008074:Lipoproteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding; D021382:Protein Sorting Signals / Q000235:genetics; D021381:Protein Transport; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008074:Lipoproteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; D000069816:SEC Translocation Channels; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D001120:Arginine; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins