1
|
Qian Y, Jiang Z, He Y, Zhang S, Jiang S. Multi-scale error feedback network for low-light image enhancement. Neural Comput Appl 2022. [DOI: 10.1007/s00521-022-07612-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
2
|
Hershko Rimon A, Livnah O, Rozman Grinberg I, Ortiz de Ora L, Yaniv O, Lamed R, Bayer EA, Frolow F, Voronov-Goldman M. Novel clostridial cell-surface hemicellulose-binding CBM3 proteins. Acta Crystallogr F Struct Biol Commun 2021; 77:95-104. [PMID: 33830074 PMCID: PMC8034430 DOI: 10.1107/s2053230x21002764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Accepted: 03/15/2021] [Indexed: 11/10/2022] Open
Abstract
A novel member of the family 3 carbohydrate-binding modules (CBM3s) is encoded by a gene (Cthe_0271) in Clostridium thermocellum which is the most highly expressed gene in the bacterium during its growth on several types of biomass substrates. Surprisingly, CtCBM3-0271 binds to at least two different types of xylan, instead of the common binding of CBM3s to cellulosic substrates. CtCBM3-0271 was crystallized and its three-dimensional structure was solved and refined to a resolution of 1.8 Å. In order to learn more about the role of this type of CBM3, a comparative study with its orthologue from Clostridium clariflavum (encoded by the Clocl_1192 gene) was performed, and the three-dimensional structure of CcCBM3-1192 was determined to 1.6 Å resolution. Carbohydrate binding by CcCBM3-1192 was found to be similar to that by CtCBM3-0271; both exhibited binding to xylan rather than to cellulose. Comparative structural analysis of the two CBM3s provided a clear functional correlation of structure and binding, in which the two CBM3s lack the required number of binding residues in their cellulose-binding strips and thus lack cellulose-binding capabilities. This is an enigma, as CtCBM3-0271 was reported to be a highly expressed protein when the bacterium was grown on cellulose. An additional unexpected finding was that CcCBM3-1192 does not contain the calcium ion that was considered to play a structural stabilizing role in the CBM3 family. Despite the lack of calcium, the five residues that form the calcium-binding site are conserved. The absence of calcium results in conformational changes in two loops of the CcCBM3-1192 structure. In this context, superposition of the non-calcium-binding CcCBM3-1192 with CtCBM3-0271 and other calcium-binding CBM3s reveals a much broader two-loop region in the former compared with CtCBM3-0271.
Collapse
Affiliation(s)
- Almog Hershko Rimon
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
- The Daniella Rich Institute for Structural Biology Research, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Oded Livnah
- The Wolfson Center for Applied and Structural Biology, Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel
| | - Inna Rozman Grinberg
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
- The Daniella Rich Institute for Structural Biology Research, Tel Aviv University, Ramat Aviv 69978, Israel
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Lizett Ortiz de Ora
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
- Department of Chemistry, University of California, Irvine, CA 92697, USA
| | - Oren Yaniv
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Raphael Lamed
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
- The Daniella Rich Institute for Structural Biology Research, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Edward A. Bayer
- Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 760001, Israel
- Department of Life Sciences and the National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva 8499000, Israel
| | - Felix Frolow
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
- The Daniella Rich Institute for Structural Biology Research, Tel Aviv University, Ramat Aviv 69978, Israel
| | - Milana Voronov-Goldman
- The Shmunis School of Biomedicine and Cancer Research, Tel Aviv University, Ramat Aviv 69978, Israel
- The Daniella Rich Institute for Structural Biology Research, Tel Aviv University, Ramat Aviv 69978, Israel
| |
Collapse
|
3
|
Kumar K, Singh S, Sharma K, Goyal A. Computational modeling and small-angle X-ray scattering based structure analysis and identifying ligand cleavage mechanism by processive endocellulase of family 9 glycoside hydrolase (HtGH9) from Hungateiclostridium thermocellum ATCC 27405. J Mol Graph Model 2020; 103:107808. [PMID: 33248343 DOI: 10.1016/j.jmgm.2020.107808] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 11/13/2020] [Accepted: 11/13/2020] [Indexed: 11/16/2022]
Abstract
The cellulases of family 9 glycoside hydrolase with subtle difference in amino acid sequence have shown different types of catalytic activities such as endo-, exo- or processive endocellulase. However, the reason behind the different types of catalytic activities still unclear. In this study, the processive endocellulase, HtGH9 of family 9 GH from Hungateiclostridium thermocellum was modeled by homology modeling. The catalytic module (HtGH9t) of HtGH9 modeled structure displayed the (α/α)6 barrel topology and associated family 3 carbohydrate binding module (HtCBM3c) displayed β-sandwich fold. Ramachandran plot of HtGH9 modeled structure displayed all the amino acid residues in allowed region except Asn225 and Asp317. Secondary structure analysis of modeled HtGH9 showed the presence of 41.3% α-helices and 11.0% β-strands which was validated through circular dichroism analysis that showed the presence of 42.6% α-helices and 14.5% β-strands. Molecular Dynamic (MD) simulation of HtGH9 structure for 50 ns showed Root Mean Square Deviation (RMSD), 0.84 nm and radius of gyration (Rg) 3.1 nm. The Small-angle X-ray scattering of HtGH9 confirmed the monodisperse state. The radius of gyration for globular shape (Rg) was 5.50 ± 0.15 nm and for rod shape (Rc) by Guinier plot was 2.0 nm. The loop formed by amino acid residues, 264-276 towards one end of the catalytic site of HtGH9 forms a barrier, that blocks the non-reducing end of the cellulose chain causing the processive cleavage resulting in the release of cellotetraose. The position of the corresponding loop in cellulases of family 9 GH is responsible for different types of cleavage patterns.
Collapse
Affiliation(s)
- Krishan Kumar
- Carbohydrate Enzyme Biotechnology Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India
| | - Shubha Singh
- Division of Biological Sciences and Engineering, Netaji Subhas University of Technology, Delhi, 110078, India
| | - Kedar Sharma
- Carbohydrate Enzyme Biotechnology Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India; Laboratory of Small Molecules & Macro Molecular Crystallography, Department of Bioengineering, Indian Institute of Technology Gandhinagar, Gandhinagar, 382355, India
| | - Arun Goyal
- Carbohydrate Enzyme Biotechnology Laboratory, Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781039, Assam, India.
| |
Collapse
|
4
|
Barbosa FC, Silvello MA, Goldbeck R. Cellulase and oxidative enzymes: new approaches, challenges and perspectives on cellulose degradation for bioethanol production. Biotechnol Lett 2020; 42:875-884. [DOI: 10.1007/s10529-020-02875-4] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 01/10/2020] [Accepted: 01/13/2020] [Indexed: 01/04/2023]
|
5
|
A novel multifunctional GH9 enzyme from Paenibacillus curdlanolyticus B-6 exhibiting endo/exo functions of cellulase, mannanase and xylanase activities. Appl Microbiol Biotechnol 2020; 104:2079-2096. [DOI: 10.1007/s00253-020-10388-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 01/07/2020] [Accepted: 01/16/2020] [Indexed: 12/13/2022]
|
6
|
Li S, Shao N, Luo Y, Liu H, Cai S, Dong X. Transcriptome and Zymogram Analyses Reveal a Cellobiose-Dose Related Reciprocal Regulatory Effect on Cellulase Synthesis in Cellulosilyticum ruminicola H1. Front Microbiol 2017; 8:2497. [PMID: 29312203 PMCID: PMC5733062 DOI: 10.3389/fmicb.2017.02497] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Accepted: 11/30/2017] [Indexed: 11/21/2022] Open
Abstract
The rumen bacterium Cellulosilyticum ruminicola H1 efficiently hydrolyzes cellulose. To gain insights into the regulatory mechanisms of cellulase synthesis, comparative transcriptome analysis was conducted for cultures grown on 2% filter paper, 0.5 and 0.05% cellobiose, and 0.5% birchwood xylan. It was found that cellulose induced a majority of (hemi)cellulases, including 33 cellulases and a cellulosomal scaffoldin (1.3- to 22.7-fold); seven endoxylanases, two mannanases, and two pectatelyases (2- to 16-fold); and pyruvate formate-lyase (PFL, 1.5- to 7-fold). Noticeably, 3- and 2.5-fold increased transcription of a cellobiohydrolase and the cellulosomal scaffoldin precursor were detected in 0.05% than in 0.5% cellobiose. Consistently, 9- and 4-fold higher specific cellobiohydrolase activities were detected in the filter paper and 0.05% cellobiose culture. SDS- and native-PAGE zymograms of cellulose-enriched proteins from the filter paper culture displayed cellulase activities, and cellulolytic “complexes” were enriched from the filter paper- and 0.05% cellobiose-cultures, but not from the 0.5% cellobiose culture. LC-MS/MS identified the cellulosomal scaffoldin precursor in the “complexes” in addition to cellulase, hemicellulase, and PFL proteins. The addition of 0.5% cellobiose, but not 0.05% cellobiose remarkably inhibited strain H1 to degrade filter paper. Therefore, this work reveals a cellobiose-dose related regulatory mechanism of cellulase synthesis by lower for induction and higher for repression, which has extended our understanding of the regulation of microbial cellulase synthesis.
Collapse
Affiliation(s)
- Shanzhen Li
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Microbial Resources, University of Chinese Academy of Sciences, Beijing, China
| | - Nana Shao
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,State Key Laboratory of Microbial Resources, University of Chinese Academy of Sciences, Beijing, China
| | - Yuanming Luo
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Hongcan Liu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Shichun Cai
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Xiuzhu Dong
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| |
Collapse
|
7
|
Impact of Module-X2 and Carbohydrate Binding Module-3 on the catalytic activity of associated glycoside hydrolases towards plant biomass. Sci Rep 2017. [PMID: 28623337 PMCID: PMC5473887 DOI: 10.1038/s41598-017-03927-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Cellulolytic enzymes capable of hydrolyzing plant biomass are secreted by microbial cells specifically in response to the carbon substrate present in the environment. These enzymes consist of a catalytic domain, generally appended to one or more non-catalytic Carbohydrate Binding Module (CBM), which enhances their activity towards recalcitrant biomass. In the present study, the genome of a cellulolytic microbe Paenibacillus polymyxa A18 was annotated for the presence of CBMs and analyzed their expression in response to the plant biomass and model polysaccharides Avicel, CMC and xylan using quantitative PCR. A gene that encodes X2-CBM3 was found to be maximally induced in response to the biomass and crystalline substrate Avicel. Association of X2-CBM3 with xyloglucanase and endoglucanase led to up to 4.6-fold increase in activity towards insoluble substrates. In the substrate binding study, module X2 showed a higher affinity towards biomass and phosphoric acid swollen cellulose, whereas CBM3 showed a higher affinity towards Avicel. Further structural modeling of X2 also indicated its potential role in substrate binding. Our findings highlighted the role of module X2 along with CBM3 in assisting the enzyme catalysis of agricultural residue and paved the way to engineer glycoside hydrolases for superior activity.
Collapse
|
8
|
Identification of a novel family of carbohydrate-binding modules with broad ligand specificity. Sci Rep 2016; 6:19392. [PMID: 26765840 PMCID: PMC4725902 DOI: 10.1038/srep19392] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 11/03/2015] [Indexed: 11/13/2022] Open
Abstract
Most enzymes that act on carbohydrates include non-catalytic carbohydrate-binding modules (CBMs) that recognize and target carbohydrates. CBMs bring their appended catalytic modules into close proximity with the target substrate and increase the hydrolytic rate of enzymes acting on insoluble substrates. We previously identified a novel CBM (CBMC5614-1) at the C-terminus of endoglucanase C5614-1 from an uncultured microorganism present in buffalo rumen. In the present study, that the functional region of CBMC5614-1 involved in ligand binding was localized to 134 amino acids. Two representative homologs of CBMC5614-1, sharing the same ligand binding profile, targeted a range of β-linked polysaccharides that adopt very different conformations. Targeted substrates included soluble and insoluble cellulose, β-1,3/1,4-mixed linked glucans, xylan, and mannan. Mutagenesis revealed that three conserved aromatic residues (Trp-380, Tyr-411, and Trp-423) play an important role in ligand recognition and targeting. These results suggest that CBMC5614-1 and its homologs form a novel CBM family (CBM72) with a broad ligand-binding specificity. CBM72 members can provide new insight into CBM-ligand interactions and may have potential in protein engineering and biocatalysis.
Collapse
|
9
|
Dhar H, Kasana RC, Gulati A. Heterologous expression and characterization of detergent stable endoglucanase EG5B from Paenibacillus sp. IHB B 3084. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.molcatb.2015.06.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
|
10
|
Ghosh A, Verma AK, Gautam S, Gupta MN, Goyal A. Structure and functional investigation of ligand binding by a family 35 carbohydrate binding module (CtCBM35) of β-mannanase of family 26 glycoside hydrolase from Clostridium thermocellum. BIOCHEMISTRY (MOSCOW) 2014; 79:672-86. [DOI: 10.1134/s0006297914070098] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
11
|
Synergism of glycoside hydrolase secretomes from two thermophilic bacteria cocultivated on lignocellulose. Appl Environ Microbiol 2014; 80:2592-601. [PMID: 24532065 DOI: 10.1128/aem.00295-14] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Two cellulolytic thermophilic bacterial strains, CS-3-2 and CS-4-4, were isolated from decayed cornstalk by the addition of growth-supporting factors to the medium. According to 16S rRNA gene-sequencing results, these strains belonged to the genus Clostridium and showed 98.87% and 98.86% identity with Clostridium stercorarium subsp. leptospartum ATCC 35414(T) and Clostridium cellulosi AS 1.1777(T), respectively. The endoglucanase and exoglucanase activities of strain CS-4-4 were approximately 3 to 5 times those of strain CS-3-2, whereas the β-glucosidase activity of strain CS-3-2 was 18 times higher than that of strain CS-4-4. The xylanase activity of strain CS-3-2 was 9 times that of strain CS-4-4, whereas the β-xylosidase activity of strain CS-4-4 was 27 times that of strain CS-3-2. The enzyme activities in spent cultures following cocultivation of the two strains with cornstalk as the substrate were much greater than those in pure cultures or an artificial mixture of samples, indicating synergism of glycoside hydrolase secretomes between the two strains. Quantitative measurement of the two strains in the cocultivation system indicated that strain CS-3-2 grew robustly during the initial stages, whereas strain CS-4-4 dominated the system in the late-exponential phase. Liquid chromatography-tandem mass spectrometry analysis of protein bands appearing in the native zymograms showed that ORF3880 and ORF3883 from strain CS-4-4 played key roles in the lignocellulose degradation process. Both these open reading frames (ORFs) exhibited endoglucanase and xylanase activities, but ORF3880 showed tighter adhesion to insoluble substrates at 4, 25, and 60°C owing to its five carbohydrate-binding modules (CBMs).
Collapse
|
12
|
Yaniv O, Fichman G, Borovok I, Shoham Y, Bayer EA, Lamed R, Shimon LJW, Frolow F. Fine-structural variance of family 3 carbohydrate-binding modules as extracellular biomass-sensing components of Clostridium thermocellum anti-σI factors. ACTA ACUST UNITED AC 2014; 70:522-34. [PMID: 24531486 DOI: 10.1107/s139900471302926x] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Accepted: 10/23/2013] [Indexed: 11/11/2022]
Abstract
The anaerobic, thermophilic, cellulosome-producing bacterium Clostridium thermocellum relies on a variety of carbohydrate-active enzymes in order to efficiently break down complex carbohydrates into utilizable simple sugars. The regulation mechanism of the cellulosomal genes was unknown until recently, when genomic analysis revealed a set of putative operons in C. thermocellum that encode σI factors (i.e. alternative σ factors that control specialized regulon activation) and their cognate anti-σI factor (RsgI). These putative anti-σI-factor proteins have modules that are believed to be carbohydrate sensors. Three of these modules were crystallized and their three-dimensional structures were solved. The structures show a high overall degree of sequence and structural similarity to the cellulosomal family 3 carbohydrate-binding modules (CBM3s). The structures of the three carbohydrate sensors (RsgI-CBM3s) and a reference CBM3 are compared in the context of the structural determinants for the specificity of cellulose and complex carbohydrate binding. Fine structural variations among the RsgI-CBM3s appear to result in alternative substrate preferences for each of the sensors.
Collapse
Affiliation(s)
- Oren Yaniv
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Galit Fichman
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Ilya Borovok
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Yuval Shoham
- Department of Biotechnology and Food Engineering, Technion - Israel Institute of Technology, Haifa, Israel
| | - Edward A Bayer
- Department of Biological Chemistry, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Raphael Lamed
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, 69978 Tel Aviv, Israel
| | - Linda J W Shimon
- Department of Chemical Research Support, The Weizmann Institute of Science, 76100 Rehovot, Israel
| | - Felix Frolow
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, 69978 Tel Aviv, Israel
| |
Collapse
|
13
|
Ghosh A, Luís AS, Brás JLA, Pathaw N, Chrungoo NK, Fontes CMGA, Goyal A. Deciphering ligand specificity of a Clostridium thermocellum family 35 carbohydrate binding module (CtCBM35) for gluco- and galacto- substituted mannans and its calcium induced stability. PLoS One 2013; 8:e80415. [PMID: 24324599 PMCID: PMC3855759 DOI: 10.1371/journal.pone.0080415] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Accepted: 10/02/2013] [Indexed: 11/25/2022] Open
Abstract
This study investigated the role of CBM35 from Clostridium thermocellum (CtCBM35) in polysaccharide recognition. CtCBM35 was cloned into pET28a (+) vector with an engineered His6 tag and expressed in Escherichia coli BL21 (DE3) cells. A homogenous 15 kDa protein was purified by immobilized metal ion chromatography (IMAC). Ligand binding analysis of CtCBM35 was carried out by affinity electrophoresis using various soluble ligands. CtCBM35 showed a manno-configured ligand specific binding displaying significant association with konjac glucomannan (Ka = 14.3×10(4) M(-1)), carob galactomannan (Ka = 12.4×10(4) M(-1)) and negligible association (Ka = 12 µM(-1)) with insoluble mannan. Binding of CtCBM35 with polysaccharides which was calcium dependent exhibited two fold higher association in presence of 10 mM Ca(2+) ion with konjac glucomannan (Ka = 41×10(4) M(-1)) and carob galactomannan (Ka = 30×10(4) M(-1)). The polysaccharide binding was further investigated by fluorescence spectrophotometric studies. On binding with carob galactomannan and konjac glucomannan the conformation of CtCBM35 changed significantly with regular 21 nm peak shifts towards lower quantum yield. The degree of association (K a) with konjac glucomannan and carob galactomannan, 14.3×10(4) M(-1) and 11.4×10(4) M(-1), respectively, corroborated the findings from affinity electrophoresis. The association of CtCBM35with konjac glucomannan led to higher free energy of binding (ΔG) -25 kJ mole(-1) as compared to carob galactomannan (ΔG) -22 kJ mole(-1). On binding CtCBM35 with konjac glucomannan and carob galactomannan the hydrodynamic radius (RH) as analysed by dynamic light scattering (DLS) study, increased to 8 nm and 6 nm, respectively, from 4.25 nm in absence of ligand. The presence of 10 mM Ca(2+) ions imparted stiffer orientation of CtCBM35 particles with increased RH of 4.52 nm. Due to such stiffer orientation CtCBM35 became more thermostable and its melting temperature was shifted to 70°C from initial 50°C.
Collapse
Affiliation(s)
- Arabinda Ghosh
- Department of Biotechnology, Indian Institute of Technology Guwahati, Guwahati, Assam, India
| | - Ana Sofia Luís
- CIISA-Faculdade de Medicina Veterinaria, Avenida da Universidade Técnica, Lisbon, Portugal
| | - Joana L. A. Brás
- CIISA-Faculdade de Medicina Veterinaria, Avenida da Universidade Técnica, Lisbon, Portugal
| | - Neeta Pathaw
- North Eastern Hill University, Shillong, Meghalaya, India
| | | | - Carlos M. G. A. Fontes
- CIISA-Faculdade de Medicina Veterinaria, Avenida da Universidade Técnica, Lisbon, Portugal
| | - Arun Goyal
- Department of Biotechnology, Indian Institute of Technology Guwahati, Guwahati, Assam, India
| |
Collapse
|
14
|
Biochemical and mutational analyses of a multidomain cellulase/mannanase from Caldicellulosiruptor bescii. Appl Environ Microbiol 2012; 78:2230-40. [PMID: 22247178 DOI: 10.1128/aem.06814-11] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Thermophilic cellulases and hemicellulases are of significant interest to the biofuel industry due to their perceived advantages over their mesophilic counterparts. We describe here biochemical and mutational analyses of Caldicellulosiruptor bescii Cel9B/Man5A (CbCel9B/Man5A), a highly thermophilic enzyme. As one of the highly secreted proteins of C. bescii, the enzyme is likely to be critical to nutrient acquisition by the bacterium. CbCel9B/Man5A is a modular protein composed of three carbohydrate-binding modules flanked at the N terminus and the C terminus by a glycoside hydrolase family 9 (GH9) module and a GH5 module, respectively. Based on truncational analysis of the polypeptide, the cellulase and mannanase activities within CbCel9B/Man5A were assigned to the N- and C-terminal modules, respectively. CbCel9B/Man5A and its truncational mutants, in general, exhibited a pH optimum of ∼5.5 and a temperature optimum of 85°C. However, at this temperature, thermostability was very low. After 24 h of incubation at 75°C, the wild-type protein maintained 43% activity, whereas a truncated mutant, TM1, maintained 75% activity. The catalytic efficiency with phosphoric acid swollen cellulose as a substrate for the wild-type protein was 7.2 s(-1) ml/mg, and deleting the GH5 module led to a mutant (TM1) with a 2-fold increase in this kinetic parameter. Deletion of the GH9 module also increased the apparent k(cat) of the truncated mutant TM5 on several mannan-based substrates; however, a concomitant increase in the K(m) led to a decrease in the catalytic efficiencies on all substrates. These observations lead us to postulate that the two catalytic activities are coupled in the polypeptide.
Collapse
|