title: Lipid chain selectivity by outer membrane phospholipase A.
abstract: Outer membrane phospholipase A (OMPLA) is a unique, integral membrane enzyme found in Gram-negative bacteria and is an important virulence factor for pathogens such as Helicobacter pylori. This broad-specificity lipase degrades a variety of lipid substrates, and it plays a direct role in adjusting the composition and permeability of bacterial membranes under conditions of stress. Interestingly, OMPLA shows little preference for the lipid headgroup and, instead, the length of the hydrophobic acyl chain is the strongest determinant for substrate selection by OMPLA, with the enzyme strongly preferring substrates with chains equal to or longer than 14 carbon atoms. The question remains as to how a hydrophobic protein like OMPLA can achieve this specificity, particularly when the shorter chains can be accommodated in the binding pocket. Using a series of sulfonyl fluoride inhibitors with various lengths of acyl chain, we show here that the thermodynamics of substrate-induced OMPLA dimerization are guided by the acyl chain length, demonstrating that OMPLA uses a unique biophysical mechanism to select its phospholipid substrate.
authors.affiliation: T.C. Jenkins Department of Biophysics, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA.
authors.forename: Ann Marie
authors.initials: AM
authors.lastname: Stanley
authors.forename: Anthony M
authors.initials: AM
authors.lastname: Treubrodt
authors.forename: Pitak
authors.initials: P
authors.lastname: Chuawong
authors.forename: Tamara L
authors.initials: TL
authors.lastname: Hendrickson
authors.forename: Karen G
authors.initials: KG
authors.lastname: Fleming
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D001665:Binding Sites; D002384:Catalysis; D004789:Enzyme Activation; D057927:Hydrophobic and Hydrophilic Interactions; D008055:Lipids; D015394:Molecular Structure; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054466:Phospholipases A1; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013441:Sulfinic Acids / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D008055:Lipids; D013441:Sulfinic Acids; C048899:sulfuryl fluoride; D010741:Phospholipases A; D054466:Phospholipases A1; C412876:outer membrane phospholipase A