Search citation statements
Paper Sections
Citation Types
Year Published
Publication Types
Relationship
Authors
Journals
Proteolysis is regulated by inactive (latent) zymogens, with a prosegment preventing access of substrates to the activesite cleft of the enzyme. How latency is maintained often depends on the catalytic mechanism of the protease. For example, in several families of the metzincin metallopeptidases, a "cysteine switch" mechanism involves a conserved prosegment motif with a cysteine residue that coordinates the catalytic zinc ion. Another family of metzincins, the astacins, do not possess a cysteine switch, so latency is maintained by other means. We have solved the high resolution crystal structure of proastacin from the European crayfish, Astacus astacus. Its prosegment is the shortest structurally reported for a metallopeptidase, and it has a unique structure. It runs through the active-site cleft in reverse orientation to a genuine substrate. Moreover, a conserved aspartate, projected by a wide loop of the prosegment, coordinates the zinc ion instead of the catalytic solvent molecule found in the mature enzyme. Activation occurs through two-step limited proteolysis and entails major rearrangement of a flexible activation domain, which becomes rigid and creates the base of the substrate-binding cleft. Maturation also requires the newly formed N terminus to be precisely trimmed so that it can participate in a buried solvent-mediated hydrogen-bonding network, which includes an invariant active-site residue. We describe a novel mechanism for latency and activation, which shares some common features both with other metallopeptidases and with serine peptidases.The proteolytic activity of most metallopeptidases (MPs) 3 is regulated, and it is only exerted where and when required (1). Such control may occur through modulation of gene expression, compartmentalization, allostery, or inhibition by protein inhibitors. Another regulatory mechanism is zymogenic latency, which is provided by mostly N-terminal prosegments. These block access of substrates to the active-site cleft, and they are removed by limited proteolysis during maturation (2, 3). Such prosegments often fold independently and guide on their part the folding process of the cognate protease domains. They may also act as intramolecular chaperones or inhibitors of the mature enzymes in trans and in intracellular sorting of the zymogen (2). Therefore, the study of the molecular mechanisms by which MPs maintain latency is indispensable to an understanding of their basic mode of action. It also paves the way for the design of inhibitors that mimic the latent state so as to modulate MP activity as part of therapeutic approaches. Detailed three-dimensional structural information can contribute much to this understanding (4). However, among the MPs, only funnelins, lysostaphins, thermolysins, and matrix metalloproteinases (MMPs) have been structurally analyzed for their zymogens. Results reveal that the mature enzyme moieties are already in a competent conformation. Notwithstanding, each group displays a distinct mechanism of latency maintenance (5-11).The metzincins...
Proteolysis is regulated by inactive (latent) zymogens, with a prosegment preventing access of substrates to the activesite cleft of the enzyme. How latency is maintained often depends on the catalytic mechanism of the protease. For example, in several families of the metzincin metallopeptidases, a "cysteine switch" mechanism involves a conserved prosegment motif with a cysteine residue that coordinates the catalytic zinc ion. Another family of metzincins, the astacins, do not possess a cysteine switch, so latency is maintained by other means. We have solved the high resolution crystal structure of proastacin from the European crayfish, Astacus astacus. Its prosegment is the shortest structurally reported for a metallopeptidase, and it has a unique structure. It runs through the active-site cleft in reverse orientation to a genuine substrate. Moreover, a conserved aspartate, projected by a wide loop of the prosegment, coordinates the zinc ion instead of the catalytic solvent molecule found in the mature enzyme. Activation occurs through two-step limited proteolysis and entails major rearrangement of a flexible activation domain, which becomes rigid and creates the base of the substrate-binding cleft. Maturation also requires the newly formed N terminus to be precisely trimmed so that it can participate in a buried solvent-mediated hydrogen-bonding network, which includes an invariant active-site residue. We describe a novel mechanism for latency and activation, which shares some common features both with other metallopeptidases and with serine peptidases.The proteolytic activity of most metallopeptidases (MPs) 3 is regulated, and it is only exerted where and when required (1). Such control may occur through modulation of gene expression, compartmentalization, allostery, or inhibition by protein inhibitors. Another regulatory mechanism is zymogenic latency, which is provided by mostly N-terminal prosegments. These block access of substrates to the active-site cleft, and they are removed by limited proteolysis during maturation (2, 3). Such prosegments often fold independently and guide on their part the folding process of the cognate protease domains. They may also act as intramolecular chaperones or inhibitors of the mature enzymes in trans and in intracellular sorting of the zymogen (2). Therefore, the study of the molecular mechanisms by which MPs maintain latency is indispensable to an understanding of their basic mode of action. It also paves the way for the design of inhibitors that mimic the latent state so as to modulate MP activity as part of therapeutic approaches. Detailed three-dimensional structural information can contribute much to this understanding (4). However, among the MPs, only funnelins, lysostaphins, thermolysins, and matrix metalloproteinases (MMPs) have been structurally analyzed for their zymogens. Results reveal that the mature enzyme moieties are already in a competent conformation. Notwithstanding, each group displays a distinct mechanism of latency maintenance (5-11).The metzincins...
The mono‐zinc endopeptidase astacin (EC 3.4.24.21) is a prototype for the astacin family and for the metzincin superfamily of metalloproteinases. Some astacins are digestive enzymes of invertebrates, but the majority serve functions during embryonic development, pattern formation, and epithelial differentiation throughout the animal kingdom. The catalytic protease domain of the astacins is topologically similar to the corresponding domains of the matrix metalloproteinases (MMPs), the adamalysins/reprolysins/ADAMs (a disintegrin and metalloprotease), the bacterial serralysins, and several other groups of zinc peptidases. They have in common a conserved zinc binding sequence, HEXXHXXGXXH, containing three histidines and a catalytically important glutamic acid residue, which acts as a general base during catalysis. Furthermore, there is a strictly conserved methionine‐containing turn structure beneath the active site, the Met‐turn, which gave rise to the designation metzincins for this superfamily of metalloproteins. In astacin, in addition to the three histidine residues of the zinc binding motif, the metal is ligated by the Glu93‐bound ‘activated’ water and by Tyr149, positioned in the Met‐turn, resulting in a trigonal bipyramidal coordination sphere. This overview treats the structural basis for the function of astacin‐like proteases, including proenzyme activation, cleavage specificity, substrate and inhibitor kinetics, catalysis, and metal binding. It also pinpoints shared commonalities and subtle differences between astacin and other metzincins.
Substrate cleavage by metalloproteinases involves nucleophilic attack on the scissile peptide bond by a water molecule that is polarized by a catalytic metal, usually a zinc ion, and a general base, usually the carboxyl group of a glutamic acid side chain. The zinc ion is most often complexed by imidazole nitrogens of histidine side chains. This arrangement suggests that the physiological pH optimum of most metalloproteinases is in the neutral range. In addition to their catalytic metal ion, many metalloproteinases contain additional transition metal or alkaline earth ions, which are structurally important or modulate the catalytic activity. As a consequence, these enzymes are generally sensitive to metal chelators. Moreover, the catalytic metal can be displaced by adventitious metal ions from buffers or biological fluids, which may fundamentally alter the catalytic function. Therefore, handling, purification, and assaying of metalloproteinases require specific precautions to warrant their stability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.