A serine protease triad forms the catalytic centre of a triacylglycerol lipase.
TL;DR: The X-ray structure of the Mucor miehei triglyceride lipase is reported and the atomic model obtained reveals a Ser .. His .. Asp trypsin-like catalytic triad with an active serine buried under a short helical fragment of a long surface loop.
Abstract: True lipases attach triacylglycerols and act at an oil-water interface; they constitute a ubiquitous group of enzymes catalysing a wide variety of reactions, many with industrial potential. But so far the three-dimensional structure has not been reported for any lipase. Here we report the X-ray structure of the Mucor miehei triglyceride lipase and describe the atomic model obtained at 3.1 A resolution and refined to 1.9 A resolution. It reveals a Ser..His..Asp trypsin-like catalytic triad with an active serine buried under a short helical fragment of a long surface loop.
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TL;DR: In all cases, enzyme engineering via immobilization techniques is perfectly compatible with other chemical or biological approaches to improve enzyme functions and the final success depend on the availability of a wide battery of immobilization protocols.
3,016 citations
TL;DR: Modeling of acetylcholine binding to the enzyme suggests that the quaternary ammonium ion is bound not to a negatively charged "anionic" site, but rather to some of the 14 aromatic residues that line the gorge.
Abstract: The three-dimensional structure of acetylcholinesterase from Torpedo californica electric organ has been determined by x-ray analysis to 2.8 angstrom resolution. The form crystallized is the glycolipid-anchored homodimer that was purified subsequent to solubilization with a bacterial phosphatidylinositol-specific phospholipase C. The enzyme monomer is an alpha/beta protein that contains 537 amino acids. It consists of a 12-stranded mixed beta sheet surrounded by 14 alpha helices and bears a striking resemblance to several hydrolase structures including dienelactone hydrolase, serine carboxypeptidase-II, three neutral lipases, and haloalkane dehalogenase. The active site is unusual because it contains Glu, not Asp, in the Ser-His-acid catalytic triad and because the relation of the triad to the rest of the protein approximates a mirror image of that seen in the serine proteases. Furthermore, the active site lies near the bottom of a deep and narrow gorge that reaches halfway into the protein. Modeling of acetylcholine binding to the enzyme suggests that the quaternary ammonium ion is bound not to a negatively charged "anionic" site, but rather to some of the 14 aromatic residues that line the gorge.
2,489 citations
TL;DR: An overview of the different PHA biosynthetic systems and their genetic background is provided, followed by a detailed summation of how this natural diversity is being used to develop commercially attractive, recombinant processes for the large-scale production of PHAs.
Abstract: Poly(3-hydroxyalkanoates) (PHAs) are a class of microbially produced polyesters that have potential applications as conventional plastics, specifically thermoplastic elastomers. A wealth of biological diversity in PHA formation exists, with at least 100 different PHA constituents and at least five different dedicated PHA biosynthetic pathways. This diversity, in combination with classical microbial physiology and modern molecular biology, has now opened up this area for genetic and metabolic engineering to develop optimal PHA-producing organisms. Commercial processes for PHA production were initially developed by W. R. Grace in the 1960s and later developed by Imperial Chemical Industries, Ltd., in the United Kingdom in the 1970s and 1980s. Since the early 1990s, Metabolix Inc. and Monsanto have been the driving forces behind the commercial exploitation of PHA polymers in the United States. The gram-negative bacterium Ralstonia eutropha, formerly known as Alcaligenes eutrophus, has generally been used as the production organism of choice, and intracellular accumulation of PHA of over 90% of the cell dry weight have been reported. The advent of molecular biological techniques and a developing environmental awareness initiated a renewed scientific interest in PHAs, and the biosynthetic machinery for PHA metabolism has been studied in great detail over the last two decades. Because the structure and monomeric composition of PHAs determine the applications for each type of polymer, a variety of polymers have been synthesized by cofeeding of various substrates or by metabolic engineering of the production organism. Classical microbiology and modern molecular bacterial physiology have been brought together to decipher the intricacies of PHA metabolism both for production purposes and for the unraveling of the natural role of PHAs. This review provides an overview of the different PHA biosynthetic systems and their genetic background, followed by a detailed summation of how this natural diversity is being used to develop commercially attractive, recombinant processes for the large-scale production of PHAs.
1,540 citations
TL;DR: In this article, the authors propose a method to identify the root cause of a problem.Abbreviations: [2]... ].., [3]
1,147 citations
1,075 citations
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TL;DR: The Protein Data Bank is a computer-based archival file for macromolecular structures that stores in a uniform format atomic co-ordinates and partial bond connectivities, as derived from crystallographic studies.
7,983 citations
TL;DR: An analysis of the solvent content of 116 different crystal forms of globular proteins found that in many cases this range will be sufficiently restrictive to enable the probable number of molecules in the crystallographic asymmetric unit to be determined directly from the molecular weight of the protein and the space group and unit cell dimensions of the crystal.
7,857 citations
TL;DR: A model building and refinement system is described for use with a Vector General 3400 display that has been used to assist in difference Fourier map interpretation at medium and high resolution, and to build a protein molecule into a multiple isomorphous replacement phased electron density map.
Abstract: A model building and refinement system is described for use with a Vector General 3400 display. The system allows the user to build models using guide atoms and angles to arrive at the final conformation. It has been used to assist in difference Fourier map interpretation at medium and high resolution, and to build a protein molecule into a multiple isomorphous replacement phased electron density map.
1,820 citations
TL;DR: Some extensions of the current export versions of the programs that have been implemented or are envisioned are described, expected to be important in realizing the goal of producing refined structural models that reproduce the diffraction patterns to within the accuracy of the measured data and which are compatible with prior stereochemical knowledge of macromolecules.
Abstract: Publisher Summary The chapter focuses on the practical application of stereochemically-restrained refinement to macromolecular crystals. Details of computational procedures and minimization algorithms are treated and need not be considered in routine applications. However, it is important to understand the nature of the function being minimized. Thorough structural refinement has become an integral part of macromolecular crystallography. The chapter describes some extensions of the current export versions of the programs that have been implemented or are envisioned. Atomic motion and conformational heterogeneity (or disorder) is major impediments to successful refinement. The use of Fourier transformations to compute structure factors and gradient vectors might greatly improve speed for large problems. There are numerous other improvements that can be envisioned including a method for modeling the fluid solvent, an appropriate treatment of the correlation between occupancy and thermal parameters of discrete solvent molecules, restraints for nonbonded contacts from crystal packing, inclusion of attractive potentials for nonbonded contacts, provision for refining partial structures, and proper estimation of standard deviations. Extensions such as these are expected to be important in realizing the goal of producing refined structural models that reproduce the diffraction patterns to within the accuracy of the measured data and which are compatible with prior stereochemical knowledge of macromolecules.
558 citations
TL;DR: Analysis of the sequence indicates that human lipoprotein lipase, hepaticlipase, and pancreatic lipase are members of a gene family that acts to hydrolyze triglycerides, providing free fatty acids for cells and affecting the maturation of circulating lipoproteins.
Abstract: Lipoprotein lipase is a key enzyme of lipid metabolism that acts to hydrolyze triglycerides, providing free fatty acids for cells and affecting the maturation of circulating lipoproteins. It has been proposed that the enzyme plays a role in the development of obesity and atherosclerosis. The human enzyme has been difficult to purify and its protein sequence was heretofore undetermined. A complementary DNA for human lipoprotein lipase that codes for a mature protein of 448 amino acids has now been cloned and sequenced. Analysis of the sequence indicates that human lipoprotein lipase, hepatic lipase, and pancreatic lipase are members of a gene family. Two distinct species of lipoprotein lipase messenger RNA that arise from alternative sites of 3'-terminal polyadenylation were detected in several different tissues.
459 citations