1
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Tanaka Y, Uchihashi T, Nakamura A. Product inhibition slow down the moving velocity of processive chitinase and sliding-intermediate state blocks re-binding of product. Arch Biochem Biophys 2024; 752:109854. [PMID: 38081338 DOI: 10.1016/j.abb.2023.109854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2023] [Revised: 11/23/2023] [Accepted: 12/06/2023] [Indexed: 12/18/2023]
Abstract
Processive movement is the key reaction for crystalline polymer degradation by enzyme. Product release is an important phenomenon in resetting the moving cycle, but how it affects chitinase kinetics was unknown. Therefore, we investigated the effect of diacetyl chitobiose (C2) on the biochemical activity and movement of chitinase A from Serratia marcescens (SmChiA). The apparent inhibition constant of C2 on crystalline chitin degradation of SmChiA was 159 μM. The binding position of C2 obtained by X-ray crystallography was at subsite +1, +2 and Trp275 interact with C2 at subsite +1. This binding state is consistent with the competitive inhibition obtained by biochemical analysis. The apparent inhibition constant of C2 on the moving velocity of high-speed (HS) AFM observations was 330 μM, which is close to the biochemical results, indicating that the main factor in crystalline chitin degradation is also the decrease in degradation activity due to inhibition of processive movement. The Trp275 is a key residue for making a sliding intermediate complex. SmChiA W275A showed weaker activity and affinity than WT against crystalline chitin because it is less processive than WT. In addition, biochemical apparent inhibition constant for C2 of SmChiA W275A was 45.6 μM. W275A mutant showed stronger C2 inhibition than WT even though the C2 binding affinity is weaker than WT. This result indicated that Trp275 is important for the interaction at subsite +1, but also important for making sliding intermediate complex and physically block the rebinding of C2 on the catalytic site for crystalline chitin degradation.
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Affiliation(s)
- Yoshiko Tanaka
- Department of Agriculture, Graduate School of Integrated Science and Technology, Shizuoka University, 836 Ohya,Suruga-ku, Shizuoka, 422-8529, Japan
| | - Takayuki Uchihashi
- Department of Physics, Nagoya University, Aichi, 464-8602, Japan; Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Higashiyama 5-1, Myodaiji, Okazaki, 444-0864, Japan
| | - Akihiko Nakamura
- Department of Applied Life Sciences, Faculty of Agriculture, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka, 422-8529, Japan; Research Institute of Green Science and Technology, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka, 422-8529, Japan; Shizuoka Institute for the Study of Marine Biology and Chemistry, Shizuoka, Shizuoka, 422-8529, Japan; Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama Myodaijicho, Okazaki, Aichi, 444-8787, Japan.
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2
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Yappert R, Peters B. Processive Depolymerization Catalysts: A Population Balance Model for Chemistry’s “While” Loop. ACS Catal 2022. [DOI: 10.1021/acscatal.2c01195] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Ryan Yappert
- Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Baron Peters
- Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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3
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Nasrin SR, Ganser C, Nishikawa S, Kabir AMR, Sada K, Yamashita T, Ikeguchi M, Uchihashi T, Hess H, Kakugo A. Deformation of microtubules regulates translocation dynamics of kinesin. SCIENCE ADVANCES 2021; 7:eabf2211. [PMID: 34644102 PMCID: PMC10763888 DOI: 10.1126/sciadv.abf2211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 08/20/2021] [Indexed: 06/13/2023]
Abstract
Microtubules, the most rigid components of the cytoskeleton, can be key transduction elements between external forces and the cellular environment. Mechanical forces induce microtubule deformation, which is presumed to be critical for the mechanoregulation of cellular events. However, concrete evidence is lacking. In this work, with high-speed atomic force microscopy, we unravel how microtubule deformation regulates the translocation of the microtubule-associated motor protein kinesin-1, responsible for intracellular transport. Our results show that the microtubule deformation by bending impedes the translocation dynamics of kinesins along them. Molecular dynamics simulation shows that the hindered translocation of kinesins can be attributed to an enhanced affinity of kinesins to the microtubule structural units in microtubules deformed by bending. This study advances our understanding of the role of cytoskeletal components in mechanotransduction.
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Affiliation(s)
| | - Christian Ganser
- Department of Creative Research, Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
| | - Seiji Nishikawa
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | | | - Kazuki Sada
- Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
| | - Takefumi Yamashita
- Laboratory for Systems Biology and Medicine, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo 153-8904, Japan
| | - Mitsunori Ikeguchi
- Graduate School of Medical Life Science, Yokohama City University, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Takayuki Uchihashi
- Department of Creative Research, Exploratory Research Center on Life and Living Systems, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
- Department of Physics, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan
| | - Henry Hess
- Department of Biomedical Engineering, Columbia University, New York, NY 10027, USA
| | - Akira Kakugo
- Faculty of Science, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-0810, Japan
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4
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Nakamura A, Kobayashi N, Koga N, Iino R. Positive Charge Introduction on the Surface of Thermostabilized PET Hydrolase Facilitates PET Binding and Degradation. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01204] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Akihiko Nakamura
- Department of Applied Life Sciences, Faculty of Agriculture, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan
- Shizuoka Institute for the Study of Marine Biology and Chemistry, Shizuoka, Shizuoka, 422-8529, Japan
| | - Naoya Kobayashi
- Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi 444-8585, Japan
| | - Nobuyasu Koga
- Exploratory Research Center on Life and Living Systems (ExCELLS), National Institutes of Natural Sciences, Okazaki, Aichi 444-8585, Japan
- Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
- School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0193, Japan
| | - Ryota Iino
- Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
- School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0193, Japan
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5
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Ando J, Kawagoe H, Nakamura A, Iino R, Fujita K. Label-free monitoring of crystalline chitin hydrolysis by chitinase based on Raman spectroscopy. Analyst 2021; 146:4087-4094. [PMID: 34060547 DOI: 10.1039/d1an00581b] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We demonstrate a method for label-free monitoring of hydrolytic activity of crystalline-chitin-degrading enzyme, chitinase, by means of Raman spectroscopy. We found that crystalline chitin exhibited a characteristic Raman peak at 2995 cm-1, which did not appear in the reaction product, N,N'-diacetylchitobiose. We used this Raman peak as a marker of crystalline chitin degradation to monitor the hydrolytic activity of chitinase. When the crystalline chitin suspension and chitinase were mixed together, the peak intensity of crystalline chitin at 2995 cm-1 was linearly decreased depending on incubation time. The decrease in peak intensity was inversely correlated with the increase in the amount of released N,N'-diacetylchitobiose, which was measured by conventional colorimetric assay with alkaline ferricyanide. Our result, presented here, provides a new method for simple, in situ, and label-free monitoring of enzymatic activity of chitinase.
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Affiliation(s)
- Jun Ando
- Department of Applied Physics, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. and Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan and Department of Functional Molecular Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
| | - Hiroyuki Kawagoe
- Department of Applied Physics, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Akihiko Nakamura
- Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan and Department of Functional Molecular Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan and Department of Applied Life Sciences, Shizuoka University, Shizuoka, Shizuoka 422-8529, Japan
| | - Ryota Iino
- Institute for Molecular Science, National Institutes of Natural Sciences, 5-1 Higashiyama, Myodaiji, Okazaki, Aichi 444-8787, Japan and Department of Functional Molecular Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
| | - Katsumasa Fujita
- Department of Applied Physics, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. and Advanced Photonics and Biosensing Open Innovation Laboratory, AIST-Osaka University, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan and Institute for Open and Transdisciplinary Research Initiatives, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
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6
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Qu M, Watanabe-Nakayama T, Sun S, Umeda K, Guo X, Liu Y, Ando T, Yang Q. High-Speed Atomic Force Microscopy Reveals Factors Affecting the Processivity of Chitinases during Interfacial Enzymatic Hydrolysis of Crystalline Chitin. ACS Catal 2020. [DOI: 10.1021/acscatal.0c02751] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Mingbo Qu
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, China
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Beijing 100193, China
| | | | - Shaopeng Sun
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, China
| | - Kenichi Umeda
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Xiaoxi Guo
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, China
| | - Yuansheng Liu
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, China
| | - Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Qing Yang
- School of Bioengineering, Dalian University of Technology, No. 2, Linggong Road, Dalian 116024, China
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, No. 2 West Yuanmingyuan Road, Beijing 100193, China
- Guangdong Laboratory for Lingnan Modern Agriculture (Shenzhen Branch), Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, No. 7 Pengfei Road, Shenzhen 518120, China
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7
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Visootsat A, Nakamura A, Wang TW, Iino R. Combined Approach to Engineer a Highly Active Mutant of Processive Chitinase Hydrolyzing Crystalline Chitin. ACS OMEGA 2020; 5:26807-26816. [PMID: 33111007 PMCID: PMC7581260 DOI: 10.1021/acsomega.0c03911] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Accepted: 09/25/2020] [Indexed: 05/08/2023]
Abstract
Serratia marcescens chitinase A (SmChiA) processively hydrolyzes recalcitrant biomass crystalline chitin under mild conditions. Here, we combined multiple sequence alignment, site-saturation mutagenesis, and automated protein purification and activity measurement with liquid-handling robot to reduce the number of mutation trials and shorten the screening time for hydrolytic activity improvement of SmChiA. The amino acid residues, which are not conserved in the alignment and are close to the aromatic residues along the substrate-binding sites in the crystal structure, were selected for site-saturation mutagenesis. Using the previously identified highly active F232W/F396W mutant as a template, we identified the F232W/F396W/S538V mutant, which shows further improved hydrolytic activity just by trying eight different sites. Importantly, valine was not found in the multiple sequence alignment at Ser538 site of SmChiA. Our combined approach allows engineering of highly active enzyme mutants, which cannot be identified only by the introduction of predominant amino acid residues in the multiple sequence alignment.
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Affiliation(s)
- Akasit Visootsat
- Department
of Functional Molecular Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
- Institute
for Molecular Science, National Institutes
of Natural Sciences, Okazaki, Aichi 444-8787, Japan
| | - Akihiko Nakamura
- Department
of Applied Life Sciences, Faculty of Agriculture, Shizuoka University, Shizuoka, Shizuoka 422-8529, Japan
| | | | - Ryota Iino
- Department
of Functional Molecular Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa 240-0193, Japan
- Institute
for Molecular Science, National Institutes
of Natural Sciences, Okazaki, Aichi 444-8787, Japan
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8
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Nakamura A, Ishiwata D, Visootsat A, Uchiyama T, Mizutani K, Kaneko S, Murata T, Igarashi K, Iino R. Domain architecture divergence leads to functional divergence in binding and catalytic domains of bacterial and fungal cellobiohydrolases. J Biol Chem 2020; 295:14606-14617. [PMID: 32816991 PMCID: PMC7586223 DOI: 10.1074/jbc.ra120.014792] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 08/15/2020] [Indexed: 01/09/2023] Open
Abstract
Cellobiohydrolases directly convert crystalline cellulose into cellobiose and are of biotechnological interest to achieve efficient biomass utilization. As a result, much research in the field has focused on identifying cellobiohydrolases that are very fast. Cellobiohydrolase A from the bacterium Cellulomonas fimi (CfCel6B) and cellobiohydrolase II from the fungus Trichoderma reesei (TrCel6A) have similar catalytic domains (CDs) and show similar hydrolytic activity. However, TrCel6A and CfCel6B have different cellulose-binding domains (CBDs) and linkers: TrCel6A has a glycosylated peptide linker, whereas CfCel6B's linker consists of three fibronectin type 3 domains. We previously found that TrCel6A's linker plays an important role in increasing the binding rate constant to crystalline cellulose. However, it was not clear whether CfCel6B's linker has similar function. Here we analyze kinetic parameters of CfCel6B using single-molecule fluorescence imaging to compare CfCel6B and TrCel6A. We find that CBD is important for initial binding of CfCel6B, but the contribution of the linker to the binding rate constant or to the dissociation rate constant is minor. The crystal structure of the CfCel6B CD showed longer loops at the entrance and exit of the substrate-binding tunnel compared with TrCel6A CD, which results in higher processivity. Furthermore, CfCel6B CD showed not only fast surface diffusion but also slow processive movement, which is not observed in TrCel6A CD. Combined with the results of a phylogenetic tree analysis, we propose that bacterial cellobiohydrolases are designed to degrade crystalline cellulose using high-affinity CBD and high-processivity CD.
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Affiliation(s)
- Akihiko Nakamura
- Department of Applied Life Sciences, Faculty of Agriculture, Shizuoka University, Shizuoka, Shizuoka, Japan.
| | - Daiki Ishiwata
- Department of Functional Molecular Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa, Japan; Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
| | - Akasit Visootsat
- Department of Functional Molecular Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa, Japan; Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
| | - Taku Uchiyama
- Department of Biomaterials Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Kenji Mizutani
- Graduate School of Medical Life Science, Yokohama City University, Tsurumi, Yokohama, Japan
| | - Satoshi Kaneko
- Department of Subtropical Biochemistry and Biotechnology, Faculty of Agriculture, University of the Ryukyus, Nishihara, Okinawa, Japan
| | - Takeshi Murata
- Department of Chemistry, Graduate School of Science, Chiba University, Inage, Chiba, Japan
| | - Kiyohiko Igarashi
- Department of Biomaterials Sciences, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Ryota Iino
- Department of Functional Molecular Science, School of Physical Sciences, SOKENDAI (The Graduate University for Advanced Studies), Hayama, Kanagawa, Japan; Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi, Japan.
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9
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Okazaki KI, Nakamura A, Iino R. Chemical-State-Dependent Free Energy Profile from Single-Molecule Trajectories of Biomolecular Motors: Application to Processive Chitinase. J Phys Chem B 2020; 124:6475-6487. [DOI: 10.1021/acs.jpcb.0c02698] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- Kei-ichi Okazaki
- Department of Theoretical and Computational Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, 444-8585, Japan
| | - Akihiko Nakamura
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, 444-8787, Japan
- Department of Applied Life Sciences, Faculty of Agriculture, Shizuoka University, Shizuoka, 422-8529, Japan
| | - Ryota Iino
- Department of Life and Coordination-Complex Molecular Science, Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, 444-8787, Japan
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10
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Nakamura A, Okazaki KI, Furuta T, Sakurai M, Ando J, Iino R. Crystalline chitin hydrolase is a burnt-bridge Brownian motor. Biophys Physicobiol 2020; 17:51-58. [PMID: 33173714 PMCID: PMC7593131 DOI: 10.2142/biophysico.bsj-2020004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 05/27/2020] [Indexed: 12/01/2022] Open
Abstract
Motor proteins are essential units of life and are well-designed nanomachines working under thermal fluctuations. These proteins control moving direction by consuming chemical energy or by dissipating electrochemical potentials. Chitinase A from bacterium Serratia marcescens (SmChiA) processively moves along crystalline chitin by hydrolysis of a single polymer chain to soluble chitobiose. Recently, we directly observed the stepping motions of SmChiA labeled with a gold nanoparticle by dark-field scattering imaging to investigate the moving mechanism. Time constants analysis revealed that SmChiA moves back and forth along the chain freely, because forward and backward states have a similar free energy level. The similar probabilities of forward-step events (83.5%=69.3%+14.2%) from distributions of step sizes and chain-hydrolysis (86.3%=(1/2.9)/(1/2.9+1/18.3)×100) calculated from the ratios of time constants of hydrolysis and the backward step indicated that SmChiA moves forward as a result of shortening of the chain by a chitobiose unit, which stabilizes the backward state. Furthermore, X-ray crystal structures of sliding intermediate and molecular dynamics simulations showed that SmChiA slides forward and backward under thermal fluctuation without large conformational changes of the protein. Our results demonstrate that SmChiA is a burnt-bridge Brownian ratchet motor.
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Affiliation(s)
| | | | - Tadaomi Furuta
- Tokyo Institute of Technology, Yokohama, Kanagawa 226-8501, Japan
| | - Minoru Sakurai
- Tokyo Institute of Technology, Yokohama, Kanagawa 226-8501, Japan
| | - Jun Ando
- RIKEN, Wako, Saitama 351-0198, Japan
| | - Ryota Iino
- Institute for Molecular Science, Okazaki, Aichi 444-8787, Japan.,SOKENDAI, Hayama, Kanagawa 240-0193, Japan
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11
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Barad BA, Liu L, Diaz RE, Basilio R, Van Dyken SJ, Locksley RM, Fraser JS. Differences in the chitinolytic activity of mammalian chitinases on soluble and insoluble substrates. Protein Sci 2020; 29:966-977. [PMID: 31930591 PMCID: PMC7096708 DOI: 10.1002/pro.3822] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 01/02/2020] [Accepted: 01/07/2020] [Indexed: 12/24/2022]
Abstract
Chitin is an abundant polysaccharide used by many organisms for structural rigidity and water repulsion. As such, the insoluble crystalline structure of chitin poses significant challenges for enzymatic degradation. Acidic mammalian chitinase, a processive glycosyl hydrolase, is the primary enzyme involved in the degradation of environmental chitin in mammalian lungs. Mutations to acidic mammalian chitinase have been associated with asthma, and genetic deletion in mice increases morbidity and mortality with age. We initially set out to reverse this phenotype by engineering hyperactive acidic mammalian chitinase variants. Using a screening approach with commercial fluorogenic substrates, we identified mutations with consistent increases in activity. To determine whether the activity increases observed were consistent with more biologically relevant chitin substrates, we developed new assays to quantify chitinase activity with insoluble chitin, and identified a one-pot fluorogenic assay that is sufficiently sensitive to quantify changes to activity due to the addition or removal of a carbohydrate-binding domain. We show that the activity increases from our directed evolution screen were lost when insoluble substrates were used. In contrast, naturally occurring gain-of-function mutations gave similar results with oligomeric and insoluble substrates. We also show that activity differences between acidic mammalian chitinase and chitotriosidase are reduced with insoluble substrate, suggesting that previously reported activity differences with oligomeric substrates may have been driven by differential substrate specificity. These results highlight the need for assays against physiological substrates when engineering metabolic enzymes, and provide a new one-pot assay that may prove to be broadly applicable to engineering glycosyl hydrolases.
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Affiliation(s)
- Benjamin A. Barad
- Department of Bioengineering and Therapeutic SciencesUniversity of CaliforniaSan FranciscoCalifornia
- Biophysics Graduate ProgramUniversity of CaliforniaSan FranciscoCalifornia
| | - Lin Liu
- Department of Bioengineering and Therapeutic SciencesUniversity of CaliforniaSan FranciscoCalifornia
| | - Roberto E. Diaz
- Department of Bioengineering and Therapeutic SciencesUniversity of CaliforniaSan FranciscoCalifornia
- Tetrad Graduate ProgramUniversity of CaliforniaSan FranciscoCalifornia
| | - Ralp Basilio
- Department of Bioengineering and Therapeutic SciencesUniversity of CaliforniaSan FranciscoCalifornia
- Science Education Partnership High School Intern Program, University of CaliforniaSan FranciscoCalifornia
| | - Steven J. Van Dyken
- Department of Pathology and ImmunologyWashington University School of Medicine in St. LouisSt. LouisMissouri
| | - Richard M. Locksley
- Department of MedicineUniversity of CaliforniaSan FranciscoCalifornia
- Department of Microbiology and ImmunologyUniversity of CaliforniaSan FranciscoCalifornia
- Howard Hughes Medical InstituteSan FranciscoCalifornia
| | - James S. Fraser
- Department of Bioengineering and Therapeutic SciencesUniversity of CaliforniaSan FranciscoCalifornia
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12
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Visootsat A, Nakamura A, Vignon P, Watanabe H, Uchihashi T, Iino R. Single-molecule imaging analysis reveals the mechanism of a high-catalytic-activity mutant of chitinase A from Serratia marcescens. J Biol Chem 2020; 295:1915-1925. [PMID: 31924658 PMCID: PMC7029130 DOI: 10.1074/jbc.ra119.012078] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 01/03/2020] [Indexed: 12/17/2022] Open
Abstract
Chitin degradation is important for biomass conversion and has potential applications for agriculture, biotechnology, and the pharmaceutical industry. Chitinase A from the Gram-negative bacterium Serratia marcescens (SmChiA) is a processive enzyme that hydrolyzes crystalline chitin as it moves linearly along the substrate surface. In a previous study, the catalytic activity of SmChiA against crystalline chitin was found to increase after the tryptophan substitution of two phenylalanine residues (F232W and F396W), located at the entrance and exit of the substrate binding cleft of the catalytic domain, respectively. However, the mechanism underlying this high catalytic activity remains elusive. In this study, single-molecule fluorescence imaging and high-speed atomic force microscopy were applied to understand the mechanism of this high-catalytic-activity mutant. A reaction scheme including processive catalysis was used to reproduce the properties of SmChiA WT and F232W/F396W, in which all of the kinetic parameters were experimentally determined. High activity of F232W/F396W mutant was caused by a high processivity and a low dissociation rate constant after productive binding. The turnover numbers for both WT and F232W/F396W, determined by the biochemical analysis, were well-replicated using the kinetic parameters obtained from single-molecule imaging analysis, indicating the validity of the reaction scheme. Furthermore, alignment of amino acid sequences of 258 SmChiA-like proteins revealed that tryptophan, not phenylalanine, is the predominant amino acid at the corresponding positions (Phe-232 and Phe-396 for SmChiA). Our study will be helpful for understanding the kinetic mechanisms and further improvement of crystalline chitin hydrolytic activity of SmChiA mutants.
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Affiliation(s)
- Akasit Visootsat
- Department of Functional Molecular Science, School of Physical Sciences, Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0193, Japan; Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
| | - Akihiko Nakamura
- Department of Functional Molecular Science, School of Physical Sciences, Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0193, Japan; Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
| | - Paul Vignon
- Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan; Chimie ParisTech, Paris 75231, France
| | - Hiroki Watanabe
- Department of Physics, Nagoya University, Nagoya, Aichi 464-8601, Japan; Exploratory Research Center on Life and Living Systems (ExCELLS), National Institute of Natural Science, Okazaki, Aichi 444-8787, Japan
| | - Takayuki Uchihashi
- Department of Physics, Nagoya University, Nagoya, Aichi 464-8601, Japan; Exploratory Research Center on Life and Living Systems (ExCELLS), National Institute of Natural Science, Okazaki, Aichi 444-8787, Japan
| | - Ryota Iino
- Department of Functional Molecular Science, School of Physical Sciences, Graduate University for Advanced Studies (SOKENDAI), Hayama, Kanagawa 240-0193, Japan; Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan.
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13
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Wang YJ, Jiang WX, Zhang YS, Cao HY, Zhang Y, Chen XL, Li CY, Wang P, Zhang YZ, Song XY, Li PY. Structural Insight Into Chitin Degradation and Thermostability of a Novel Endochitinase From the Glycoside Hydrolase Family 18. Front Microbiol 2019; 10:2457. [PMID: 31736903 PMCID: PMC6831621 DOI: 10.3389/fmicb.2019.02457] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 10/14/2019] [Indexed: 01/25/2023] Open
Abstract
Bacterial endochitinases play important roles in environmental chitin degradation and have good applications. Although the structures of some endochitinases, most belonging to the glycoside hydrolase (GH) family 18 and thermostable, have been reported, the structural basis of these enzymes for chitin degradation still remain unclear due to the lack of functional confirmation, and the molecular mechanism for their thermostability is also unknown. Here, we characterized a GH18 endochitinase, Chi23, from marine bacterium Pseudoalteromonas aurantia DSM6057, and solved its structure. Chi23 is a thermostable enzyme that can non-processively hydrolyze crystalline and colloidal chitin. Chi23 contains only a catalytic domain that adopts a classical (β/α)8 TIM-barrel fold. Compared to other GH18 bacterial endochitinases, Chi23 lacks the chitin-binding domain and the β-hairpin subdomain, indicating that Chi23 has a novel structure. Based on structural analysis of Chi23 docked with (GlcNAc)5 and mutational analysis, the key catalytic residue (Glu117) and seven substrate-binding residues (Asn9, Gln157, Tyr189, Asn190, Asp229, Trp260, and Gln261) are revealed. Among these identified residues, Asn9, Asp229 and Gln261 are unique to Chi23, and their cumulative roles contribute to the activity of Chi23 against both crystalline and soluble chitin. Five substrate-binding residues (Tyr189, Asn190, Asp229, Trp260, and Gln261) are found to play important roles in maintaining the thermostability of Chi23. In particular, hydrogen bond networks involving Asp229 and Gln261 are formed to stabilize the protein structure of Chi23. Phylogenetic analysis indicated that Chi23 and its homologs represent a new group of GH18 endochitinases, which are widely distributed in bacteria. This study sheds light on the molecular mechanism of a GH18 endochitinase for chitin degradation.
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Affiliation(s)
- Yan-Jun Wang
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Wen-Xin Jiang
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Yi-Shuo Zhang
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Hai-Yan Cao
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Yi Zhang
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Xiu-Lan Chen
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Chun-Yang Li
- College of Marine Life Sciences, Institute for Advanced Ocean Study, Ocean University of China, Qingdao, China.,Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
| | - Peng Wang
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China.,College of Marine Life Sciences, Institute for Advanced Ocean Study, Ocean University of China, Qingdao, China
| | - Yu-Zhong Zhang
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China.,College of Marine Life Sciences, Institute for Advanced Ocean Study, Ocean University of China, Qingdao, China.,Laboratory for Marine Biology and Biotechnology, Pilot National Laboratory for Marine Science and Technology, Qingdao, China
| | - Xiao-Yan Song
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
| | - Ping-Yi Li
- State Key Laboratory of Microbial Technology, Marine Biotechnology Research Center, Shandong University, Qingdao, China
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14
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Umakoshi T, Fukuda S, Iino R, Uchihashi T, Ando T. High-speed near-field fluorescence microscopy combined with high-speed atomic force microscopy for biological studies. Biochim Biophys Acta Gen Subj 2019; 1864:129325. [PMID: 30890438 DOI: 10.1016/j.bbagen.2019.03.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Revised: 03/07/2019] [Accepted: 03/14/2019] [Indexed: 11/30/2022]
Abstract
BACKGROUND High-speed atomic force microscopy (HS-AFM) has successfully visualized a variety of protein molecules during their functional activity. However, it cannot visualize small molecules interacting with proteins and even protein molecules when they are encapsulated. Thus, it has been desired to achieve techniques enabling simultaneous optical/AFM imaging at high spatiotemporal resolution with high correlation accuracy. METHODS Scanning near-field optical microscopy (SNOM) is a candidate for the combination with HS-AFM. However, the imaging rate of SNOM has been far below that of HS-AFM. We here developed HS-SNOM and metal tip-enhanced total internal reflection fluorescence microscopy (TIRFM) by exploiting tip-scan HS-AFM and exploring methods to fabricate a metallic tip on a tiny HS-AFM cantilever. RESULTS In tip-enhanced TIRFM/HS-AFM, simultaneous video recording of the two modalities of images was demonstrated in the presence of fluorescent molecules in the bulk solution at relatively high concentration. By using fabricated metal-tip cantilevers together with our tip-scan HS-AFM setup equipped with SNOM optics, we could perform simultaneous HS-SNOM/HS-AFM imaging, with correlation analysis between the two overlaid images being facilitated. CONCLUSIONS This study materialized simultaneous tip-enhanced TIRFM/HS-AFM and HS-SNOM/HS-AFM imaging at high spatiotemporal resolution. Although some issues remain to be solved in the future, these correlative microscopy methods have a potential to increase the versatility of HS-AFM in biological research. GENERAL SIGNIFICANCE We achieved an imaging rate of ~3 s/frame for SNOM imaging, more than 100-times higher than the typical SNOM imaging rate. We also demonstrated ~39 nm resolution in HS-SNOM imaging of fluorescently labeled DNA in solution.
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Affiliation(s)
- Takayuki Umakoshi
- Department of Applied Physics, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Shingo Fukuda
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Ryota Iino
- Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi 444-8787, Japan
| | - Takayuki Uchihashi
- Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Toshio Ando
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
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15
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Nakamura A, Iino R. Visualization of Functional Structure and Kinetic Dynamics of Cellulases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2018; 1104:201-217. [PMID: 30484250 DOI: 10.1007/978-981-13-2158-0_10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Affiliation(s)
- Akihiko Nakamura
- Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Aichi, Japan.
- Department of Functional Molecular Science, School of Physical Sciences, Kanagawa, Japan.
| | - Ryota Iino
- Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Aichi, Japan
- Department of Functional Molecular Science, School of Physical Sciences, Kanagawa, Japan
- Institute for Molecular Science, National Institutes of Natural Sciences, Aichi, Japan
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16
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Ando J, Nakamura A, Visootsat A, Yamamoto M, Song C, Murata K, Iino R. Single-Nanoparticle Tracking with Angstrom Localization Precision and Microsecond Time Resolution. Biophys J 2018; 115:2413-2427. [PMID: 30527446 PMCID: PMC6302141 DOI: 10.1016/j.bpj.2018.11.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 11/12/2018] [Accepted: 11/13/2018] [Indexed: 11/16/2022] Open
Abstract
Gold nanoparticles (AuNPs) have been used as a contrast agent for optical imaging of various single biomolecules. Because AuNPs have high scattering efficiency without photobleaching, biomolecular dynamics have been observed with nanometer localization precision and sub-millisecond time resolution. To understand the working principle of biomolecular motors in greater detail, further improvement of the localization precision and time resolution is necessary. Here, we investigated the lower limit of localization precision achievable with AuNPs and the fundamental law, which determines the localization precision. We first used objective-lens-type total internal reflection dark-field microscopy to obtain a scattering signal from an isolated AuNP. The localization precision was inversely proportional to the square root of the photon number, which is consistent with theoretical estimation. The lower limit of precision for a 40 nm AuNP was ∼0.3 nm with 1 ms time resolution and was restricted by detector saturation. To achieve higher localization precision, we designed and constructed an annular illumination total internal reflection dark-field microscopy system with an axicon lens, which can illuminate the AuNPs at high laser intensity without damaging the objective lens. In addition, we used high image magnification to avoid detector saturation. Consequently, we achieved 1.3 Å localization precision for 40 nm AuNPs and 1.9 Å localization precision for 30 nm AuNPs at 1 ms time resolution. Furthermore, even at 33 μs time resolution, localization precisions at 5.4 Å for 40 nm AuNPs and at 1.7 nm for 30 nm AuNPs were achieved. We then observed motion of head of kinesin-1 labeled with AuNP at microsecond time resolution. Transition cycles of bound/unbound states and tethered diffusion of unbound head during stepping motion on microtubule were clearly captured with higher time resolution or smaller AuNP than those used in previous studies, indicating applicability to single-molecule imaging of biomolecular motors.
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Affiliation(s)
- Jun Ando
- Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi, Japan; The Graduate University for Advanced Studies, Hayama, Kanagawa, Japan
| | - Akihiko Nakamura
- Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi, Japan; The Graduate University for Advanced Studies, Hayama, Kanagawa, Japan
| | - Akasit Visootsat
- Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi, Japan; The Graduate University for Advanced Studies, Hayama, Kanagawa, Japan
| | - Mayuko Yamamoto
- Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
| | - Chihong Song
- National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
| | - Kazuyoshi Murata
- National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Aichi, Japan
| | - Ryota Iino
- Institute for Molecular Science, National Institutes of Natural Sciences, Okazaki, Aichi, Japan; The Graduate University for Advanced Studies, Hayama, Kanagawa, Japan.
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17
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Nakamura A, Okazaki KI, Furuta T, Sakurai M, Iino R. Processive chitinase is Brownian monorail operated by fast catalysis after peeling rail from crystalline chitin. Nat Commun 2018; 9:3814. [PMID: 30232340 PMCID: PMC6145945 DOI: 10.1038/s41467-018-06362-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 08/29/2018] [Indexed: 12/02/2022] Open
Abstract
Processive chitinase is a linear molecular motor which moves on the surface of crystalline chitin driven by processive hydrolysis of single chitin chain. Here, we analyse the mechanism underlying unidirectional movement of Serratia marcescens chitinase A (SmChiA) using high-precision single-molecule imaging, X-ray crystallography, and all-atom molecular dynamics simulation. SmChiA shows fast unidirectional movement of ~50 nm s-1 with 1 nm forward and backward steps, consistent with the length of reaction product chitobiose. Analysis of the kinetic isotope effect reveals fast substrate-assisted catalysis with time constant of ~3 ms. Decrystallization of the single chitin chain from crystal surface is the rate-limiting step of movement with time constant of ~17 ms, achieved by binding free energy at the product-binding site of SmChiA. Our results demonstrate that SmChiA operates as a burnt-bridge Brownian ratchet wherein the Brownian motion along the single chitin chain is rectified forward by substrate-assisted catalysis.
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Grants
- JP15H06898 Ministry of Education, Culture, Sports, Science, and Technology (MEXT)
- JP17K18429 Ministry of Education, Culture, Sports, Science, and Technology (MEXT)
- JP17H05899 Ministry of Education, Culture, Sports, Science, and Technology (MEXT)
- JP16H00789 Ministry of Education, Culture, Sports, Science, and Technology (MEXT)
- JP16H00858 Ministry of Education, Culture, Sports, Science, and Technology (MEXT)
- JP17K19213 Ministry of Education, Culture, Sports, Science, and Technology (MEXT)
- JP18H05424 Ministry of Education, Culture, Sports, Science, and Technology (MEXT)
- JP15H04366 Ministry of Education, Culture, Sports, Science, and Technology (MEXT)
- 01311805 MEXT | National Institutes of Natural Sciences (NINS)
- J281002 MEXT | National Institutes of Natural Sciences (NINS)
- Advanced Technology Institute Research Grants (RG2709)
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Affiliation(s)
- Akihiko Nakamura
- Institute for Molecular Science, National Institutes of Natural Sciences, 444-8787, Okazaki, Aichi, Japan.
- Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama, 240-0193, Japan.
| | - Kei-Ichi Okazaki
- Institute for Molecular Science, National Institutes of Natural Sciences, 444-8787, Okazaki, Aichi, Japan
| | - Tadaomi Furuta
- Center for Biological Resources and Informatics, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
| | - Minoru Sakurai
- Center for Biological Resources and Informatics, Tokyo Institute of Technology, Yokohama, 226-8501, Japan
| | - Ryota Iino
- Institute for Molecular Science, National Institutes of Natural Sciences, 444-8787, Okazaki, Aichi, Japan.
- Department of Functional Molecular Science, SOKENDAI (The Graduate University for Advanced Studies), Hayama, 240-0193, Japan.
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18
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Steven J. VD, Richard M. L. Chitins and chitinase activity in airway diseases. J Allergy Clin Immunol 2018; 142:364-369. [PMID: 29959948 PMCID: PMC6078791 DOI: 10.1016/j.jaci.2018.06.017] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 06/19/2018] [Accepted: 06/22/2018] [Indexed: 01/04/2023]
Abstract
Chitin, one of the most abundant biopolymers on Earth, is bound and degraded by chitinases, specialized enzymes that are similarly widespread in nature. Chitin catabolism affects global carbon and nitrogen cycles through a host of diverse biological processes, but recent work has focused attention on systems of chitin recognition and degradation conserved in mammals, connecting an ancient pathway of polysaccharide processing to human diseases influenced by persistent immune triggering. Here we review current advances in our understanding of how chitin-chitinase interactions affect mucosal immune feedback mechanisms essential to maintaining homeostasis and organ health.
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Affiliation(s)
- Van Dyken Steven J.
- Department of Pathology & Immunology, Washington University School of Medicine, St. Louis, MO USA.
| | - Locksley Richard M.
- Howard Hughes Medical Institute, Departments of Medicine and Microbiology / Immuology, University of California San Francisco, San Francisco, CA, USA.
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19
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Kawai F, Nakamura A, Visootsat A, Iino R. Plasmid-Based One-Pot Saturation Mutagenesis and Robot-Based Automated Screening for Protein Engineering. ACS OMEGA 2018; 3:7715-7726. [PMID: 30221239 PMCID: PMC6130897 DOI: 10.1021/acsomega.8b00663] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2018] [Accepted: 06/27/2018] [Indexed: 05/24/2023]
Abstract
We evaluated a method for protein engineering using plasmid-based one-pot saturation mutagenesis and robot-based automated screening. When the biases in nucleotides and amino acids were assessed for a loss-of-function point mutation in green fluorescent protein, the ratios of gain-of-function mutants were not significantly different from the expected values for the primers among the three different suppliers. However, deep sequencing analysis revealed that the ratios of nucleotides in the primers were highly biased among the suppliers. Biases for NNB were less severe than for NNN. We applied this method to screen a fusion protein of two chitinases, ChiA and ChiB (ChiAB). Three NNB codons as well as tyrosine and serine (X1YSX2X3) were inserted to modify the surface structure of ChiAB. We observed significant amino acid bias at the X3 position in water-soluble, active ChiAB-X1YSX2X3 mutants. Examination of the crystal structure of one active mutant, ChiAB-FYSFV, revealed that the X3 residue plays an important role in structure stabilization.
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Affiliation(s)
- Fumihiro Kawai
- Institute
for Molecular Science, National Institutes
of Natural Sciences, 5-1 Higashiyama Myodaijicho, Okazaki, Aichi 444-8787, Japan
| | - Akihiko Nakamura
- Institute
for Molecular Science, National Institutes
of Natural Sciences, 5-1 Higashiyama Myodaijicho, Okazaki, Aichi 444-8787, Japan
- The
Graduate University for Advanced Studies (SOKENDAI), Shonan Village, Hayama, Kanagawa 240-0193, Japan
| | - Akasit Visootsat
- The
Graduate University for Advanced Studies (SOKENDAI), Shonan Village, Hayama, Kanagawa 240-0193, Japan
| | - Ryota Iino
- Institute
for Molecular Science, National Institutes
of Natural Sciences, 5-1 Higashiyama Myodaijicho, Okazaki, Aichi 444-8787, Japan
- The
Graduate University for Advanced Studies (SOKENDAI), Shonan Village, Hayama, Kanagawa 240-0193, Japan
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