Lipase activation by nonionic detergents. The crystal structure of the porcine lipase-colipase-tetraethylene glycol monooctyl ether complex.
The crystal structure of the ternary porcine lipase-colipase-tetra ethylene glycol monooctyl ether (TGME) complex has been determined at 2.8 A resolution. The crystals belong to the cubic space group F23 with a = 289.1 A and display a strong pseudo-symmetry corresponding to a P23 lattice. Unexpectedly, the crystalline two-domain lipase is found in its open configuration. This indicates that in the presence of colipase, pure micelles of the nonionic detergent TGME are able to activate the enzyme; a process that includes the movement of an N-terminal domain loop (the flap). The effects of TGME and colipase have been confirmed by chemical modification of the active site serine residue using diisopropyl p-nitrophenylphosphate (E600). In addition, the presence of a TGME molecule tightly bound to the active site pocket shows that TGME acts as a substrate analog, thus possibly explaining the inhibitory effect of this nonionic detergent on emulsified substrate hydrolysis at submicellar concentrations. A comparison of the lipase-colipase interactions between our porcine complex and the human-porcine complex (van Tilbeurgh, H., Egloff, M.-P., Martinez, C., Rugani, N., Verger, R., and Cambillau, C.(1993) Nature 362, 814-820) indicates that except for one salt bridge interaction, they are conserved. Analysis of the superimposed complexes shows a 5.4 degrees rotation on the relative position of the N-terminal domains excepting the flap that moves in a concerted fashion with the C-terminal domain. This flexibility may be important for the binding of the complex to the water-lipid interface.
Hermoso
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Laboratoire de Cristallographie et de Cristallogénèse des Protéines, Institut de Biologie Structurale Jean-Pierre Ebel, CEA-CNRS, Grenoble, France.
Pignol
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D
Kerfelec
B
B
Crenon
I
I
Chapus
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Fontecilla-Camps
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JC
D000818:Animals; D001665:Binding Sites; D003089:Colipases / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003902:Detergents / Q000737:chemistry*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors; D005026:Ethylene Glycols / Q000737:chemistry*; D006023:Glycoproteins / Q000737:chemistry; D008049:Lipase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D008958:Models, Molecular; D010179:Pancreas / Q000201:enzymology; D011487:Protein Conformation; D013552:Swine
D003089:Colipases; D003902:Detergents; D004791:Enzyme Inhibitors; D005026:Ethylene Glycols; D006023:Glycoproteins; D008049:Lipase