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Vaissier Welborn V. Understanding Cysteine Reactivity in Protein Environments with Electric Fields. J Phys Chem B 2023; 127:9936-9942. [PMID: 37962274 DOI: 10.1021/acs.jpcb.3c05749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
The role cysteine residues play in proteins is mediated by their protonation state, whereby the thiolate form of the side chain is highly reactive while the thiol form is more inert. However, the pKa of cysteine residues is hard to predict as it can differ widely from its reference value in solution, an effect that is accentuated by local effects in the heterogeneous protein environment. Here, we present a new approach to the prediction of cysteine reactivity based on electric field calculations at the thiol/thiolate group. We validated our approach by predicting the protonation state of cysteine residues in different protein environments (in the active site, at the protein surface, and buried within the protein interior), including Cys-25 in papaya protease omega, which was proven problematic for the more traditional constant pH molecular dynamics (MD) technique. We predict pKa shifts consistent with experimental observations, and the decomposition of the electric fields into contributions from molecular fragments provides a direct handle to rationalize local pH and pKa effects in proteins without introducing parameters other than those of the force field used for MD simulations.
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Affiliation(s)
- Valerie Vaissier Welborn
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24060, United States
- Macromolecules Innovation Institute (MII),Virginia Tech, Blacksburg, Virginia 24060, United States
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Cordara G, van Eerde A, Grahn EM, Winter HC, Goldstein IJ, Krengel U. An Unusual Member of the Papain Superfamily: Mapping the Catalytic Cleft of the Marasmius oreades agglutinin (MOA) with a Caspase Inhibitor. PLoS One 2016; 11:e0149407. [PMID: 26901797 PMCID: PMC4764322 DOI: 10.1371/journal.pone.0149407] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Accepted: 02/01/2016] [Indexed: 11/18/2022] Open
Abstract
Papain-like cysteine proteases (PLCPs) constitute the largest group of thiol-based protein degrading enzymes and are characterized by a highly conserved fold. They are found in bacteria, viruses, plants and animals and involved in a number of physiological and pathological processes, parasitic infections and host defense, making them interesting targets for drug design. The Marasmius oreades agglutinin (MOA) is a blood group B-specific fungal chimerolectin with calcium-dependent proteolytic activity. The proteolytic domain of MOA presents a unique structural arrangement, yet mimicking the main structural elements in known PLCPs. Here we present the X-ray crystal structure of MOA in complex with Z-VAD-fmk, an irreversible caspase inhibitor known to cross-react with PLCPs. The structural data allow modeling of the substrate binding geometry and mapping of the fundamental enzyme-substrate interactions. The new information consolidates MOA as a new, yet strongly atypical member of the papain superfamily. The reported complex is the first published structure of a PLCP in complex with the well characterized caspase inhibitor Z-VAD-fmk.
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Affiliation(s)
- Gabriele Cordara
- Department of Chemistry, University of Oslo, Oslo, Norway
- Department of Biochemistry, Institute for Cancer Research, The Norwegian Radium Hospital, Oslo, Norway
| | | | - Elin M. Grahn
- Department of Chemistry, University of Oslo, Oslo, Norway
| | - Harry C. Winter
- Department of Biological Chemistry, Medical School, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Irwin J. Goldstein
- Department of Biological Chemistry, Medical School, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Ute Krengel
- Department of Chemistry, University of Oslo, Oslo, Norway
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3
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Hussain S, Khan A, Gul S, Resmini M, Verma CS, Thomas EW, Brocklehurst K. Identification of interactions involved in the generation of nucleophilic reactivity and of catalytic competence in the catalytic site Cys/His ion pair of papain. Biochemistry 2011; 50:10732-42. [PMID: 22044167 DOI: 10.1021/bi201207z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Understanding the roles of noncovalent interactions within the enzyme molecule and between enzyme and substrate or inhibitor is an essential goal of the investigation of active center chemistry and catalytic mechanism. Studies on members of the papain family of cysteine proteinases, particularly papain (EC 3.4.22.2) itself, continue to contribute to this goal. The historic role of the catalytic site Cys/His ion pair now needs to be understood within the context of multiple dynamic phenomena. Movement of Trp177 may be necessary to expose His159 to solvent with consequent decrease in its degree of electrostatic solvation of (Cys25)-S(-). Here we report an investigation of this possibility using computer modeling of quasi-transition states and pH-dependent kinetics using 3,3'-dipyridazinyl disulfide, its n-propyl and phenyl derivatives, and 4,4'-dipyrimidyl disulfide as reactivity probes that differ in the location of potential hydrogen-bonding acceptor atoms. Those interactions that influence ion pair geometry and thereby catalytic competence, including by transmission of the modulatory effect of a remote ionization with pK(a) 4, were identified. A key result is the correlation between the kinetic influence of the modulatory trigger of pK(a) 4 and disruption of the hydrogen bond donated by the indole N-H of Trp177, the hydrophobic shield of the initial "intimate" ion pair. This hydrogen bond is accepted by the amide O of Gln19-a component of the oxyanion hole that binds the tetrahedral species formed from the substrate during the catalytic act. The disruption would be expected to contribute to the mobility of Trp177 and possibly to the effectiveness of the binding of the developing oxyanion.
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Affiliation(s)
- Syeed Hussain
- Laboratory of Structural and Mechanistic Enzymology, School of Biological and Chemical Sciences, Queen Mary, University of London, London E1 4NS, UK
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4
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Native and Biotechnologically Engineered Plant Proteases with Industrial Applications. FOOD BIOPROCESS TECH 2010. [DOI: 10.1007/s11947-010-0431-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Ghosh R, Chakraborty S, Chakrabarti C, Dattagupta JK, Biswas S. Structural insights into the substrate specificity and activity of ervatamins, the papain-like cysteine proteases from a tropical plant, Ervatamia coronaria. FEBS J 2007; 275:421-34. [PMID: 18167146 DOI: 10.1111/j.1742-4658.2007.06211.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Multiple proteases of the same family are quite often present in the same species in biological systems. These multiple proteases, despite having high homology in their primary and tertiary structures, show deviations in properties such as stability, activity, and specificity. It is of interest, therefore, to compare the structures of these multiple proteases in a single species to identify the structural changes, if any, that may be responsible for such deviations. Ervatamin-A, ervatamin-B and ervatamin-C are three such papain-like cysteine proteases found in the latex of the tropical plant Ervatamia coronaria, and are known not only for their high stability over a wide range of temperature and pH, but also for variations in activity and specificity among themselves and among other members of the family. Here we report the crystal structures of ervatamin-A and ervatamin-C, complexed with an irreversible inhibitor 1-[l-N-(trans-epoxysuccinyl)leucyl]amino-4-guanidinobutane (E-64), together with enzyme kinetics and molecular dynamic simulation studies. A comparison of these results with the earlier structures helps in a correlation of the structural features with the corresponding functional properties. The specificity constants (k(cat)/K(m)) for the ervatamins indicate that all of these enzymes have specificity for a branched hydrophobic residue at the P2 position of the peptide substrates, with different degrees of efficiency. A single amino acid change, as compared to ervatamin-C, in the S2 pocket of ervatamin-A (Ala67-->Tyr) results in a 57-fold increase in its k(cat)/K(m) value for a substrate having a Val at the P2 position. Our studies indicate a higher enzymatic activity of ervatamin-A, which has been subsequently explained at the molecular level from the three-dimensional structure of the enzyme and in the context of its helix polarizibility and active site plasticity.
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Affiliation(s)
- Raka Ghosh
- Crystallography and Molecular Biology Division, Saha Institute of Nuclear Physics, Kolkata, India
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6
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Theodorou LG, Bieth JG, Papamichael EM. The catalytic mode of cysteine proteinases of papain (C1) family. BIORESOURCE TECHNOLOGY 2007; 98:1931-9. [PMID: 16997546 DOI: 10.1016/j.biortech.2006.07.037] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2006] [Revised: 07/13/2006] [Accepted: 07/15/2006] [Indexed: 05/11/2023]
Abstract
The Proton Inventory (PI) method has been applied in the hydrolysis of synthetic substrates by papain, chymopapain and stem bromelain, comparing also their corresponding pH-(k(cat)/K(m)) profiles, and it was found: (a) k(cat)/K(m)=k(1), and thus K(S)=k(2)/k(1) is a dynamic equilibrium constant, (b) bowed-downward PI for k(cat)/K(m) exhibiting large inverse SIE, and (c) linear PI exhibiting large normal SIE for K(S), k(2) and k(3). A novel finding of this work is that the association of substrates onto all three studied cysteine proteinases proceeds via a stepwise pathway, in contrast to purely concerted pathways found previously for both acylation and deacylation. A hydrogen bond, which seems more likely to be developed across a pK(a)-value close to 4.00, connecting [see text] (papain/chymopapain or bromelain numbering), constitutes another novelty of this work.
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Affiliation(s)
- Leonidas G Theodorou
- University of Ioannina, Department of Chemistry, Laboratory of Biochemistry, 451-10 Ioannina, Greece
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Dardenne LE, Werneck AS, de Oliveira Neto M, Bisch PM. Electrostatic properties in the catalytic site of papain: A possible regulatory mechanism for the reactivity of the ion pair. Proteins 2003; 52:236-53. [PMID: 12833547 DOI: 10.1002/prot.10368] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
We present an analysis of the electrostatic properties in the catalytic site of papain (EC 3.4.22.2), an archetype enzyme of the C1 cysteine proteinase family, and we investigate their possible role in the formation, stabilization and regulation of the Cys25((-))...His159((+)) catalytic ion pair. The electrostatic properties were computed using a reassociation method based in multicentered multipolar expansions obtained from ab initio quantum calculations of overlapping protein fragments. Solvent effects were introduced by coupling the use of multicentered multipolar expansions to two continuum boundary element methods to solve the Poisson and the linearized Poisson-Boltzmann equations. The electrostatic profile found in the proton transfer region of papain showed that this enzyme has a well-defined electrostatic environment to favor the formation and stabilization of the catalytic ion pair. The papain catalytic site electrostatic profile can be considered as an electrostatic fingerprint of the papain family with the following characteristics: (i) the presence of a net electric field highly aligned in the (Cys25)-SG-->(His159)-ND1 direction; (ii) the electrostatic profile has a saddle-point character; (iii) it is basically a local environmental effect. Furthermore, our analysis describes a possible regulatory mechanism (the E(SG-->ND1) attenuation effect) controlling the ion pair reactivity and permits to infer the Asp57 acidic residue as the most probable candidate to act as the electrostatic modulator.
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Affiliation(s)
- Laurent E Dardenne
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro-UFRJ, CCS, Bloco G, Ilha do Fundão, 21949-900 Rio de Janeiro, RJ, Brazil
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8
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Hussain S, Pinitglang S, Bailey TSF, Reid JD, Noble MA, Resmini M, Thomas EW, Greaves RB, Verma CS, Brocklehurst K. Variation in the pH-dependent pre-steady-state and steady-state kinetic characteristics of cysteine-proteinase mechanism: evidence for electrostatic modulation of catalytic-site function by the neighbouring carboxylate anion. Biochem J 2003; 372:735-46. [PMID: 12643810 PMCID: PMC1223443 DOI: 10.1042/bj20030177] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2003] [Revised: 03/06/2003] [Accepted: 03/18/2003] [Indexed: 11/17/2022]
Abstract
The acylation and deacylation stages of the hydrolysis of N -acetyl-Phe-Gly methyl thionoester catalysed by papain and actinidin were investigated by stopped-flow spectral analysis. Differences in the forms of pH-dependence of the steady-state and pre-steady-state kinetic parameters support the hypothesis that, whereas for papain, in accord with the traditional view, the rate-determining step is the base-catalysed reaction of the acyl-enzyme intermediate with water, for actinidin it is a post-acylation conformational change required to permit release of the alcohol product and its replacement in the catalytic site by the key water molecule. Possible assignments of the kinetically influential p K (a) values, guided by the results of modelling, including electrostatic-potential calculations, and of the mechanistic roles of the ionizing groups, are discussed. It is concluded that Asp(161) is the source of a key electrostatic modulator (p K (a) 5.0+/-0.1) in actinidin, analogous to Asp(158) in papain, whose influence is not detected kinetically; it is always in the 'on' state because of its low p K (a) value (2.8+/-0.06).
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Affiliation(s)
- Syeed Hussain
- Laboratory of Structural and Mechanistic Enzymology, School of Biological Sciences, Queen Mary, University of London, Mile End Road, UK
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9
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Schlick P, Kronovetr J, Hampoelz B, Skern T. Modulation of the electrostatic charge at the active site of foot-and-mouth-disease-virus leader proteinase, an unusual papain-like enzyme. Biochem J 2002; 363:493-501. [PMID: 11964149 PMCID: PMC1222501 DOI: 10.1042/0264-6021:3630493] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The leader proteinase (L(pro)) of foot-and-mouth-disease virus is an unusual papain-like cysteine proteinase. Synthesized without an N-terminal pro precursor region, it frees itself from the growing polypeptide chain by cleavage at its own C-terminus. It also possesses a unique electrostatic environment around the active site, essentially due to Asp(163), which orients the catalytic histidine residue, and Asp(164); the equivalent residues in papain are Asn(175) and Ser(176). The importance of these residues for L(pro) activity was examined by site-directed mutagenesis. Replacement of Asp(163) with asparagine reduced activity by five-fold towards a hexapeptide substrate and slightly delayed self-processing when expressed in rabbit reticulocyte lysates. However, no effect on the cleavage of the only known cellular substrate of L(pro), eukaryotic initiation factor 4GI (eIF4GI), was observed. In contrast, replacement of Asp(164) by either alanine, asparagine or lysine abrogated activity towards the hexapeptide. Furthermore, in all cases, the onset of both self-processing and eIF4GI cleavage were significantly delayed; the reaction rates were also diminished compared with those of the wild-type enzyme. The alanine-substituted enzyme was least affected, followed by those substituted with asparagine and lysine. The double mutant protein in which both aspartate residues were replaced by asparagine was most severely affected; it failed to complete either self-processing or eIF4GI cleavage within 3 h, compared with the 8 min required by the wild-type enzyme. Hence, we propose that the electrostatic charge of Asp(164), and to a lesser extent that of Asp(163), is extremely important for L(pro) to attain full activity upon synthesis.
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Affiliation(s)
- Petra Schlick
- Institute of Medical Biochemistry, Division of Biochemistry, University of Vienna, Dr. Bohr-Gasse 9/3, A-1030 Vienna, Austria
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Neves-Petersen MT, Petersen EI, Fojan P, Noronha M, Madsen RG, Petersen SB. Engineering the pH-optimum of a triglyceride lipase: from predictions based on electrostatic computations to experimental results. J Biotechnol 2001; 87:225-54. [PMID: 11334666 DOI: 10.1016/s0168-1656(01)00240-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The optimisation of enzymes for particular purposes or conditions remains an important target in virtually all protein engineering endeavours. Here, we present a successful strategy for altering the pH-optimum of the triglyceride lipase cutinase from Fusarium solani pisi. The computed electrostatic pH-dependent potentials in the active site environment are correlated with the experimentally observed enzymatic activities. At pH-optimum a distinct negative potential is present in all the lipases and esterases that we studied so far. This has prompted us to propose the "The Electrostatic Catapult Model" as a model for product release after cleavage of the ester bond. The origin of the negative potential is associated with the titration status of specific residues in the vicinity of the active site cleft. In the case of cutinase, the role of Glu44 was systematically investigated by mutations into Ala and Lys. Also, the neighbouring Thr45 was mutated into Proline, with the aim of shifting the spatial location of Glu44. All the charge mutants displayed altered titration behaviour of active site electrostatic potentials. Typically, the substitution of the residue Glu44 pushes the onset of the active site negative potential towards more alkaline conditions. We, therefore, predicted more alkaline pH optima, and this was indeed the experimentally observed. Finally, it was found that the pH-dependent computed Coulombic energy displayed a strong correlation with the observed melting temperatures of native cutinase.
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Affiliation(s)
- M T Neves-Petersen
- The Biostructure and Protein Engineering Group, Department of Life Sciences, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark
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11
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Dunn BM, Hung S. The two sides of enzyme-substrate specificity: lessons from the aspartic proteinases. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1477:231-40. [PMID: 10708860 DOI: 10.1016/s0167-4838(99)00275-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Like most proteolytic enzymes, the aspartic proteinases bind substrates and most inhibitors within an extended active site cleft. Bound ligands typically adopt a beta-strand conformation. Interactions with groups on both sides of the cleft determine the primary as well as secondary specificity of the enzymes. We have pursued the discovery of the sometimes subtle distinctions between members of the aspartic proteinase family by two routes. In the first case, we have constructed sets of oligopeptide substrates with systematic variation in each position to assess interactions at one position at a time. In the second type of experiment, we have altered residues of the enzymes in order to test theories of selectivity. The combination of the two approaches has provided a better understanding of the forces involved in determining specificity of enzyme action.
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Affiliation(s)
- B M Dunn
- Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, P.O. Box 100245, Gainesville, FL 32610-0245, USA
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12
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Ikeuchi Y, Katerelos NA, Goodenough PW. The enhancing of a cysteine proteinase activity at acidic pH by protein engineering, the role of glutamic 50 in the enzyme mechanism of caricain. FEBS Lett 1998; 437:91-6. [PMID: 9804178 DOI: 10.1016/s0014-5793(98)01194-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Carica papaya produces four cysteine proteinases. Calculations show that the Cys25, His159 essential ion pair is fully ionised at pH 2.99, where activity cannot be detected, but apparently an additional ionisation with a pKa of 4 is essential for activity (an electrostatic switch). Caricain (EC 3.4.22.30) wt and D158E genetic backgrounds were used to study the contribution of E50A to activity. E50 or E135 are candidates for the switch, E50A would be expected to reduce activity. However, activity increased at pH 5.0 in both backgrounds and at the pH optimum in D158E E50A but decreased slightly in the wt background. This challenges the hypothesis of an electrostatic switch.
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Affiliation(s)
- Y Ikeuchi
- School of Plant Sciences, Plant Science Laboratories, University of Reading, UK
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13
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McGrath ME, Klaus JL, Barnes MG, Brömme D. Crystal structure of human cathepsin K complexed with a potent inhibitor. NATURE STRUCTURAL BIOLOGY 1997; 4:105-9. [PMID: 9033587 DOI: 10.1038/nsb0297-105] [Citation(s) in RCA: 136] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Groves MR, Taylor MA, Scott M, Cummings NJ, Pickersgill RW, Jenkins JA. The prosequence of procaricain forms an alpha-helical domain that prevents access to the substrate-binding cleft. Structure 1996; 4:1193-203. [PMID: 8939744 DOI: 10.1016/s0969-2126(96)00127-x] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND Cysteine proteases are involved in a variety of cellular processes including cartilage degradation in arthritis, the progression of Alzheimer's disease and cancer invasion: these enzymes are therefore of immense biological importance. Caricain is the most basic of the cysteine proteases found in the latex of Carica papaya. It is a member of the papain superfamily and is homologous to other plant and animal cysteine proteases. Caricain is naturally expressed as an inactive zymogen called procaricain. The inactive form of the protease contains an inhibitory proregion which consists of an additional 106 N-terminal amino acids; the proregion is removed upon activation. RESULTS The crystal structure of procaricain has been refined to 3.2 A resolution; the final model consists of three non-crystallographically related molecules. The proregion of caricain forms a separate globular domain which binds to the C-terminal domain of mature caricain. The proregion also contains an extended polypeptide chain which runs through the substrate-binding cleft, in the opposite direction to that of the substrate, and connects to the N terminus of the mature region. The mature region does not undergo any conformational change on activation. CONCLUSIONS We conclude that the rate-limiting step in the in vitro activation of procaricain is the dissociation of the prodomain, which is then followed by proteolytic cleavage of the extended polypeptide chain of the proregion. The prodomain provides a stable scaffold which may facilitate the folding of the C-terminal lobe of procaricain.
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Affiliation(s)
- M R Groves
- Department of Food Macromolecular Science, Institute of Food Research, Reading, UK
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15
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Katerelos NA, Taylor MA, Scott M, Goodenough PW, Pickersgill RW. Crystal structure of a caricain D158E mutant in complex with E-64. FEBS Lett 1996; 392:35-9. [PMID: 8769310 DOI: 10.1016/0014-5793(96)00697-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The structure of the D158E mutant of caricain (previously known as papaya protease omega) in complex with E-64 has been determined at 2.0 A resolution (overall R factor 19.3%). The structure reveals that the substituted glutamate makes the same pattern of hydrogen bonds as the aspartate in native caricain. This was not anticipated since in the native structure there is insufficient room to accommodate the glutamate side chain. The glutamate is accommodated in the mutant by a local expansion of the structure demonstrating that small structural changes are responsible for the change in activity.
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16
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Song I, Taylor M, Baker K, Bateman RC. Inhibition of cysteine proteinases by Carica papaya cystatin produced in Escherichia coli. Gene 1995; 162:221-4. [PMID: 7557432 DOI: 10.1016/0378-1119(95)00258-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
A papaya cystatin (Cst)-encoding cDNA clone was isolated from a papaya leaf cDNA library and the active protein produced in Escherichia coli. The amino-acid sequence reveals a protein of 11,262 Da with over 40% identity to other published plant Cst. Unique features of the papaya Cst include a single Cys residue, variation in the papain-binding region, and the first reported inhibition of papaya proteinase IV by a Cst.
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Affiliation(s)
- I Song
- Department of Chemistry and Biochemistry, University of Southern Mississippi, Hattiesburg 39406-5043, USA
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Abstract
In the past year, substantial progress has been made in the modeling of electrostatic interactions in biomolecules. This review highlights advances in the following areas: first, the efficient computation of long-range electrostatic interactions in detailed molecular simulations; second, the application of the Poisson-Boltzmann electrostatic model in conformational analysis; third, the application of the Poisson-Boltzmann model in quantum chemistry calculations; fourth, the development of atomic parameters; and finally, the modeling of ionization equilibria in proteins.
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Affiliation(s)
- M K Gilson
- Center for Advanced Research in Biotechnology, Rockville, USA
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