Snijder, H.J. et al. Structural evidence for dimerization-regulated activation of an integral membrane phospholipase. Nature 401, 717-721

Laboratory of Biophysical Chemistry, BIOSON Research Institute, University of Groningen, The Netherlands.
Nature (Impact Factor: 41.46). 11/1999; 401(6754):717-21. DOI: 10.1038/44890
Source: PubMed


Dimerization is a biological regulatory mechanism employed by both soluble and membrane proteins. However, there are few structural data on the factors that govern dimerization of membrane proteins. Outer membrane phospholipase A (OMPLA) is an integral membrane enzyme which participates in secretion of colicins in Escherichia coli. In Campilobacter and Helicobacter pylori strains, OMPLA is implied in virulence. Its activity is regulated by reversible dimerization. Here we report X-ray structures of monomeric and dimeric OMPLA from E. coli. Dimer interactions occur almost exclusively in the apolar membrane-embedded parts, with two hydrogen bonds within the hydrophobic membrane area being key interactions. Dimerization results in functional oxyanion holes and substrate-binding pockets, which are absent in monomeric OMPLA. These results provide a detailed view of activation by dimerization of a membrane protein.

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    • "The association of two enzymes interacting via the flat barrel side creates a dimeric complex with two extended clefts along the subunit interface that bind the substrate [57]. The architecture of the substrate binding clefts and the catalytic site allows productive binding of substrates with either one or two acyl chains of various lengths [57]. The enteric pathogen Yersinia pseudotuberculosis, which causes human gastroenteritis and mesenteric lymphadenitis, encodes an outer membrane PLase A 2 named PldA, which is active against PC and SM [58]. "
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    ABSTRACT: Bacterial sphingomyelinases and phospholipases constitute a heterogeneous group of surface associated or secreted esterases, produced by a variety of Gram-positive and Gram-negative bacteria. In several cases mutant strains lacking a gene encoding a sphingomyelinase or a phospholipase have reduced pathogenicity in experimental animals demonstrating the role of the corresponding enzyme in pathogenesis. Bacterial sphingomyelinases and phospholipases might favor in different ways the colonization of the infected tissue, the establishment and progression of the infection or the evasion of the immune response by both intracellular and extracellular pathogens. This chapter presents an overview of the classification, structure, and main physiopathological activities of bacterial sphingomyelinases and phospholipases, providing examples of their roles as virulence factors in several human and animal diseases.
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    • "The fact that the truncated OmpA-1-276 and OmpA-188-276 were also able to form dimers suggests that in the context of the dimer, the soluble domains are not integrating into this proposed 16-stranded pore. Dimerization as a mechanism to regulate an enzymatic role is also plausible, as seen for the dimeric OmpA (OmpLA) (Snijder et al., 1999). OmpA by contrast has no known enzymatic activity. "
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    ABSTRACT: The transmembrane domain of the outer membrane protein A (OmpA) from Escherichia coli is an excellent model for structural and folding studies of β-barrel membrane proteins. However, full-length OmpA resists crystallographic efforts, and the link between its function and tertiary structure remains controversial. Here we use site-directed mutagenesis and mass spectrometry of different constructs of OmpA, released in the gas phase from detergent micelles, to define the minimal region encompassing the C-terminal dimer interface. Combining knowledge of the location of the dimeric interface with molecular modeling and ion mobility data allows us to propose a low-resolution model for the full-length OmpA dimer. Our model of the dimer is in remarkable agreement with experimental ion mobility data, with none of the unfolding or collapse observed for full-length monomeric OmpA, implying that dimer formation stabilizes the overall structure and prevents collapse of the flexible linker that connects the two domains.
    Full-text · Article · Apr 2014 · Structure
    • "OMPs carry out different tasks in the membrane. They work as protein translocators and folding catalysts for other OMPs [4], adhesins for bacterial infection [5], passive diffusion pores and efflux channels [6], siderophore receptors [7] and enzymes [8] [9] [10] [11], e.g. lipases, proteases and palmitoyl transferases. "
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    ABSTRACT: Folding and stability of bacterial outer membrane proteins (OMPs) are typically studied in vitro using model systems such as phospholipid vesicles or surfactant. OMP folding requires surfactant concentrations above the critical micelle concentration (cmc) and usually only occurs in neutral or zwitterionic surfactants, but not in anionic or cationic surfactants. Various Gram-negative bacteria produce the anionic biosurfactant rhamnolipid. Here we show that the OMP OmpA can be folded in rhamnolipid at concentrations above the cmc, though the thermal stability is reduced compared to the nonionic surfactant dodecyl maltoside. We discuss implications for possible interactions between OMPs and biosurfactants in vivo.
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