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Zhao J, Zhou P, Zhang L, Liu W, Liu W, Zhang Y, Li Y, Shi Z, Gao J. N-region of Cry1Ia: A novel fusion tag for Escherichia coli and Pichia pastoris. J Biotechnol 2023; 366:54-64. [PMID: 36822476 DOI: 10.1016/j.jbiotec.2023.02.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 02/20/2023] [Accepted: 02/20/2023] [Indexed: 02/25/2023]
Abstract
Secretory signal peptides (SPs) can increase enhanced green fluorescent protein (eGFP) expression in cytosol. In this study, SPs Iasp (Cry1Ia), Vasp (Vip3A), and their local sequences were used as fusion tags to compare their effects on eGFP expression in Escherichia coli MC4100 and Pichia pastoris GS115. In E coli, the solubility was almost opposite between the proteins encoded by Vegfp and Iegfp. This may be because the overall hydrophobicity of the SPs differed. When the hydrophobic H-region and C-region were removed, the negative effects on eGFP solubility of the N-regions of both SPs (IaN and VN) were significantly reduced without compromise on the expression level. IaN promotes eGFP protein yield 7.1-fold more than Iasp, and using this peptide in tandem (Ia3N) further enhanced fluorescent fusion protein solubility with an efficacy similar to that of a polycationic tag. Furthermore, the GS-IaNeGFP strain produced the highest fluorescent signal intensity when these fusion proteins were expressed in P. pastoris, and the expression was higher than in other strains, including eGFP. In conclusion, we revealed the potential of the N-region of Iasp as a fusion tag in both prokaryotic and eukaryotic cells and further demonstrated the value of the N-regions of abundant SPs.
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Affiliation(s)
- Juanli Zhao
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong 030801, Shanxi, China
| | - Pu Zhou
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong 030801, Shanxi, China
| | - Luyao Zhang
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong 030801, Shanxi, China
| | - Wenhui Liu
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong 030801, Shanxi, China
| | - Wei Liu
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong 030801, Shanxi, China
| | - Yuqi Zhang
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong 030801, Shanxi, China
| | - Yi Li
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong 030801, Shanxi, China
| | - Zongyong Shi
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong 030801, Shanxi, China.
| | - Jianhua Gao
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong 030801, Shanxi, China.
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Gao J, Ouyang C, Zhao J, Han Y, Guo Q, Liu X, Zhang T, Duan M, Wang X, Xu C. Coexpressing the Signal Peptide of Vip3A and the Trigger Factor of Bacillus thuringiensis Enhances the Production Yield and Solubility of eGFP in Escherichia coli. Front Microbiol 2022; 13:892428. [PMID: 35923407 PMCID: PMC9342664 DOI: 10.3389/fmicb.2022.892428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 06/21/2022] [Indexed: 11/13/2022] Open
Abstract
Many fusion tags have been developed to improve the expression of recombinant proteins. Besides the translocation of cargo proteins, the signal peptides (SPs) of some secretory proteins, such as the ssTorA and Iasp, have been used as an inclusion body tag (IB-tag) or the recombinant expression enhancer in the cytosol of E. coli. In this study, the approach to utilize the SP of Vip3A (Vasp) from Bacillus thuringiensis (Bt) as a fusion tag was investigated. The results showed that either the Vasp or its predicted N- (VN), H- (VH), and C-regions (VC), as well as their combinations (VNH, VNC, and VHC), were able to significantly enhance the production yield of eGFP. However, the hydrophobic region of the Vasp (VH and/or VC) made more than half of the eGFP molecules aggregated (VeGFP, VHeGFP, VCeGFP, VNHeGFP, VNCeGFP, and VHCeGFP). Interestingly, the addition of the Bt trigger factor (BtTF) led to the neutralization of the negative impact and solubilization of the fusion proteins. Therefore, the coexpression of Vasp or its derivates with the chaperone BtTF could be a novel dual-enhancement system for the production yield and solubility of recombinant proteins. Notably, EcTF was unable to impact the solubility of Vasp or its derivates guided proteins, suggesting its different specificities on the recognition or interaction. Additionally, this study also suggested that the translocation of Vip3 in the host cell would be regulated by the BtTF-involved model.
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Affiliation(s)
- Jianhua Gao
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong, China
| | - Chunping Ouyang
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong, China
| | - Juanli Zhao
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong, China
| | - Yan Han
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong, China
| | - Qinghua Guo
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong, China
| | - Xuan Liu
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong, China
| | - Tianjiao Zhang
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong, China
| | - Ming Duan
- Experimental Teaching Center, Shanxi Agricultural University, Jinzhong, China
| | - Xingchun Wang
- Shanxi Key Laboratory of Minor Crops Germplasm Innovation and Molecular Breeding, College of Life Sciences, Shanxi Agricultural University, Jinzhong, China
- Xingchun Wang
| | - Chao Xu
- State Key Laboratory of Rice Biology, Institute of Insect Sciences, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China
- *Correspondence: Chao Xu
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Gao J, Qian H, Guo X, Mi Y, Guo J, Zhao J, Xu C, Zheng T, Duan M, Tang Z, Lin C, Shen Z, Jiang Y, Wang X. The signal peptide of Cry1Ia can improve the expression of eGFP or mCherry in Escherichia coli and Bacillus thuringiensis and enhance the host's fluorescent intensity. Microb Cell Fact 2020; 19:112. [PMID: 32448275 PMCID: PMC7247199 DOI: 10.1186/s12934-020-01371-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 05/16/2020] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND The signal peptides (SPs) of secretory proteins are frequently used or modified to guide recombinant proteins outside the cytoplasm of prokaryotic cells. In the periplasmic space and extracellular environment, recombinant proteins are kept away from the intracellular proteases and often they can fold correctly and efficiently. Consequently, expression levels of the recombinant protein can be enhanced by the presence of a SP. However, little attention has been paid to the use of SPs with low translocation efficiency for recombinant protein production. In this paper, the function of the signal peptide of Bacillus thuringiensis (Bt) Cry1Ia toxin (Iasp), which is speculated to be a weak translocation signal, on regulation of protein expression was investigated using fluorescent proteins as reporters. RESULTS When fused to the N-terminal of eGFP or mCherry, the Iasp can improve the expression of the fluorescent proteins and as a consequence enhance the fluorescent intensity of both Escherichia coli and Bt host cells. Real-time quantitative PCR analysis revealed the higher transcript levels of Iegfp over those of egfp gene in E. coli TG1 cells. By immunoblot analysis and confocal microscope observation, lower translocation efficiency of IeGFP was demonstrated. The novel fluorescent fusion protein IeGFP was then used to compare the relative strengths of cry1Ia (Pi) and cry1Ac (Pac) gene promoters in Bt strain, the latter promoter proving the stronger. The eGFP reporter, by contrast, cannot indicate unambiguously the regulation pattern of Pi at the same level of sensitivity. The fluorescent signals of E. coli and Bt cells expressing the Iasp fused mCherry (ImCherry) were also enhanced. Importantly, the Iasp can also enhanced the expression of two difficult-to-express proteins, matrix metalloprotease-13 (MMP13) and myostatin (growth differentiating factor-8, GDF8) in E. coli BL21-star (DE3) strain. CONCLUSIONS We identified the positive effects of a weak signal peptide, Iasp, on the expression of fluorescent proteins and other recombinant proteins in bacteria. The produced IeGFP and ImCherry can be used as novel fluorescent protein variants in prokaryotic cells. The results suggested the potential application of Iasp as a novel fusion tag for improving the recombinant protein expression.
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Affiliation(s)
- Jianhua Gao
- College of Life Sciences, Shanxi Agricultural University, Taigu, 030801, China.
| | - Hongmei Qian
- College of Life Sciences, Shanxi Agricultural University, Taigu, 030801, China
| | - Xiaoqin Guo
- College of Life Sciences, Shanxi Agricultural University, Taigu, 030801, China
| | - Yi Mi
- College of Life Sciences, Shanxi Agricultural University, Taigu, 030801, China
| | - Junpei Guo
- College of Life Sciences, Shanxi Agricultural University, Taigu, 030801, China
| | - Juanli Zhao
- College of Life Sciences, Shanxi Agricultural University, Taigu, 030801, China
| | - Chao Xu
- State Key Laboratory of Rice Biology, Institute of Insect Sciences, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, China
| | - Ting Zheng
- State Key Laboratory of Rice Biology, Institute of Insect Sciences, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, China
| | - Ming Duan
- Experimental Teaching Center, Shanxi Agricultural University, Taigu, 030801, China
| | - Zhongwei Tang
- College of Life Sciences, Shanxi Agricultural University, Taigu, 030801, China
| | - Chaoyang Lin
- State Key Laboratory of Rice Biology, Institute of Insect Sciences, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, China
| | - Zhicheng Shen
- State Key Laboratory of Rice Biology, Institute of Insect Sciences, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310058, China
| | - Yiwei Jiang
- Department of Agronomy, Purdue University, West Lafayette, IN, 47907, USA
| | - Xingchun Wang
- College of Life Sciences, Shanxi Agricultural University, Taigu, 030801, China.
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4
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Wu K, Stull F, Lee C, Bardwell JCA. Protein folding while chaperone bound is dependent on weak interactions. Nat Commun 2019; 10:4833. [PMID: 31645566 PMCID: PMC6811625 DOI: 10.1038/s41467-019-12774-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Accepted: 09/23/2019] [Indexed: 12/31/2022] Open
Abstract
It is generally assumed that protein clients fold following their release from chaperones instead of folding while remaining chaperone-bound, in part because binding is assumed to constrain the mobility of bound clients. Previously, we made the surprising observation that the ATP-independent chaperone Spy allows its client protein Im7 to fold into the native state while continuously bound to the chaperone. Spy apparently permits sufficient client mobility to allow folding to occur while chaperone bound. Here, we show that strengthening the interaction between Spy and a recently discovered client SH3 strongly inhibits the ability of the client to fold while chaperone bound. The more tightly Spy binds to its client, the more it slows the folding rate of the bound client. Efficient chaperone-mediated folding while bound appears to represent an evolutionary balance between interactions of sufficient strength to mediate folding and interactions that are too tight, which tend to inhibit folding. Spy is an ATP independent chaperone that allows folding of its client protein Im7 while continuously bound to Spy. Here the authors employ kinetics measurements to study the folding of another Spy client protein SH3 and find that Spy’s ability to allow a client to fold while bound is inversely related to how strongly it interacts with that client.
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Affiliation(s)
- Kevin Wu
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI, 48109-1085, USA.,Department of Biophysics, University of Michigan, Ann Arbor, MI, 48109-1055, USA
| | - Frederick Stull
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI, 48109-1085, USA.,Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109-1085, USA.,Department of Chemistry, Western Michigan University, Kalamazoo, MI, 49008-5413, USA
| | - Changhan Lee
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI, 48109-1085, USA.,Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109-1085, USA
| | - James C A Bardwell
- Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI, 48109-1085, USA. .,Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI, 48109-1085, USA.
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5
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Crane JM, Randall LL. The Sec System: Protein Export in Escherichia coli. EcoSal Plus 2017; 7:10.1128/ecosalplus.ESP-0002-2017. [PMID: 29165233 PMCID: PMC5807066 DOI: 10.1128/ecosalplus.esp-0002-2017] [Citation(s) in RCA: 61] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Indexed: 11/20/2022]
Abstract
In Escherichia coli, proteins found in the periplasm or the outer membrane are exported from the cytoplasm by the general secretory, Sec, system before they acquire stably folded structure. This dynamic process involves intricate interactions among cytoplasmic and membrane proteins, both peripheral and integral, as well as lipids. In vivo, both ATP hydrolysis and proton motive force are required. Here, we review the Sec system from the inception of the field through early 2016, including biochemical, genetic, and structural data.
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Affiliation(s)
- Jennine M. Crane
- Department of Biochemistry, University of Missouri, Columbia, Missouri
| | - Linda L. Randall
- Department of Biochemistry, University of Missouri, Columbia, Missouri
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6
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Horowitz S, Koldewey P, Stull F, Bardwell JC. Folding while bound to chaperones. Curr Opin Struct Biol 2017; 48:1-5. [PMID: 28734135 DOI: 10.1016/j.sbi.2017.06.009] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 06/23/2017] [Accepted: 06/28/2017] [Indexed: 01/08/2023]
Abstract
Chaperones are important in preventing protein aggregation and aiding protein folding. How chaperones aid protein folding remains a key question in understanding their mechanism. The possibility of proteins folding while bound to chaperones was reintroduced recently with the chaperone Spy, many years after the phenomenon was first reported with the chaperones GroEL and SecB. In this review, we discuss the salient features of folding while bound in the cases for which it has been observed and speculate about its biological importance and possible occurrence in other chaperones.
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Affiliation(s)
- Scott Horowitz
- Department of Chemistry & Biochemistry and the Knoebel Institute for Healthy Aging, University of Denver, 2155 E. Wesley Avenue, Denver, CO 80208, USA.
| | - Philipp Koldewey
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N. University, Ann Arbor, MI 48109, USA
| | - Frederick Stull
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N. University, Ann Arbor, MI 48109, USA; Howard Hughes Medical Institute, University of Michigan, 830 N. University, Ann Arbor, MI 48109, USA
| | - James Ca Bardwell
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, 830 N. University, Ann Arbor, MI 48109, USA; Howard Hughes Medical Institute, University of Michigan, 830 N. University, Ann Arbor, MI 48109, USA.
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7
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Singh P, Sharma L, Kulothungan SR, Adkar BV, Prajapati RS, Ali PSS, Krishnan B, Varadarajan R. Effect of signal peptide on stability and folding of Escherichia coli thioredoxin. PLoS One 2013; 8:e63442. [PMID: 23667620 PMCID: PMC3646739 DOI: 10.1371/journal.pone.0063442] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2012] [Accepted: 04/03/2013] [Indexed: 11/19/2022] Open
Abstract
The signal peptide plays a key role in targeting and membrane insertion of secretory and membrane proteins in both prokaryotes and eukaryotes. In E. coli, recombinant proteins can be targeted to the periplasmic space by fusing naturally occurring signal sequences to their N-terminus. The model protein thioredoxin was fused at its N-terminus with malE and pelB signal sequences. While WT and the pelB fusion are soluble when expressed, the malE fusion was targeted to inclusion bodies and was refolded in vitro to yield a monomeric product with identical secondary structure to WT thioredoxin. The purified recombinant proteins were studied with respect to their thermodynamic stability, aggregation propensity and activity, and compared with wild type thioredoxin, without a signal sequence. The presence of signal sequences leads to thermodynamic destabilization, reduces the activity and increases the aggregation propensity, with malE having much larger effects than pelB. These studies show that besides acting as address labels, signal sequences can modulate protein stability and aggregation in a sequence dependent manner.
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Affiliation(s)
- Pranveer Singh
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Likhesh Sharma
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | | | - Bharat V. Adkar
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | | | - P. Shaik Syed Ali
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Beena Krishnan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
| | - Raghavan Varadarajan
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, India
- Chemical Biology Unit, Jawaharlal NehruCentre for Advanced Scientific Research, Jakkur, Bangalore, India
- * E-mail:
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8
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Tiwari S, Kumar V, Jayaraj GG, Maiti S, Mapa K. Unique structural modulation of a non-native substrate by cochaperone DnaJ. Biochemistry 2013; 52:1011-8. [PMID: 23331070 DOI: 10.1021/bi301543g] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The role of bacterial DnaJ protein as a cochaperone of DnaK is strongly appreciated. Although DnaJ unaccompanied by DnaK can bind unfolded as well as native substrate proteins, its role as an individual chaperone remains elusive. In this study, we demonstrate that DnaJ binds a model non-native substrate with a low nanomolar dissociation constant and, more importantly, modulates the structure of its non-native state. The structural modulation achieved by DnaJ is different compared to that achieved by the DnaK-DnaJ complex. The nature of structural modulation exerted by DnaJ is suggestive of a unique unfolding activity on the non-native substrate by the chaperone. Furthermore, we demonstrate that the zinc binding motif along with the C-terminal substrate binding domain of DnaJ is necessary and sufficient for binding and the subsequent binding-induced structural alterations of the non-native substrate. We hypothesize that this hitherto unknown structural alteration of non-native states by DnaJ might be important for its chaperoning activity by removing kinetic traps of the folding intermediates.
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Affiliation(s)
- Satyam Tiwari
- Proteomics and Structural Biology Unit, CSIR-Institute of Genomics and Integrative Biology, South Campus, Mathura Road, Delhi 110020, India
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9
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Zhou Q, Sun S, Tai P, Sui SF. Structural characterization of the complex of SecB and metallothionein-labeled proOmpA by cryo-electron microscopy. PLoS One 2012; 7:e47015. [PMID: 23056562 PMCID: PMC3464278 DOI: 10.1371/journal.pone.0047015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Accepted: 09/11/2012] [Indexed: 11/19/2022] Open
Abstract
ProOmpA is a preprotein that is translocated across the plasma membrane by the general secretory pathway in Escherichia coli. The molecular chaperon SecB in Sec pathway can recognize and bind proOmpA for its translocation. However, the structure of the SecB/proOmpA complex remains unknown. Here, we constructed an uncleavable proOmpA fused with metallothionein at its C-terminus and labeled it with metals in vitro for the study of cryo-electron microscopy. Using single particle cryo-electron microscopy, we reconstructed 3D structure of the stable SecB/proOmpA complex. The structure shows that the major portion of preprotein locates on one side of SecB tetramer, resulting in an asymmetric binding pattern. This work also provides a possible approach to the structure determination of small protein complexes by cryo-electron microscopy.
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Affiliation(s)
- Qiang Zhou
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Shan Sun
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
| | - Phang Tai
- Department of Biology, Georgia State University, Atlanta, Georgia, United States of America
| | - Sen-Fang Sui
- State Key Laboratory of Biomembrane and Membrane Biotechnology, Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing, China
- * E-mail:
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10
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Aggarwal V, Kulothungan SR, Balamurali MM, Saranya SR, Varadarajan R, Ainavarapu SRK. Ligand-modulated parallel mechanical unfolding pathways of maltose-binding proteins. J Biol Chem 2011; 286:28056-65. [PMID: 21659518 DOI: 10.1074/jbc.m111.249045] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Protein folding and unfolding are complex phenomena, and it is accepted that multidomain proteins generally follow multiple pathways. Maltose-binding protein (MBP) is a large (a two-domain, 370-amino acid residue) bacterial periplasmic protein involved in maltose uptake. Despite the large size, it has been shown to exhibit an apparent two-state equilibrium unfolding in bulk experiments. Single-molecule studies can uncover rare events that are masked by averaging in bulk studies. Here, we use single-molecule force spectroscopy to study the mechanical unfolding pathways of MBP and its precursor protein (preMBP) in the presence and absence of ligands. Our results show that MBP exhibits kinetic partitioning on mechanical stretching and unfolds via two parallel pathways: one of them involves a mechanically stable intermediate (path I) whereas the other is devoid of it (path II). The apoMBP unfolds via path I in 62% of the mechanical unfolding events, and the remaining 38% follow path II. In the case of maltose-bound MBP, the protein unfolds via the intermediate in 79% of the cases, the remaining 21% via path II. Similarly, on binding to maltotriose, a ligand whose binding strength with the polyprotein is similar to that of maltose, the occurrence of the intermediate is comparable (82% via path I) with that of maltose. The precursor protein preMBP also shows a similar behavior upon mechanical unfolding. The percentages of molecules unfolding via path I are 53% in the apo form and 68% and 72% upon binding to maltose and maltotriose, respectively, for preMBP. These observations demonstrate that ligand binding can modulate the mechanical unfolding pathways of proteins by a kinetic partitioning mechanism. This could be a general mechanism in the unfolding of other large two-domain ligand-binding proteins of the bacterial periplasmic space.
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Affiliation(s)
- Vasudha Aggarwal
- Department of Biological Sciences, Tata Institute of Fundamental Research, Colaba, Mumbai 400 005, India
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11
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Bechtluft P, Kedrov A, Slotboom DJ, Nouwen N, Tans SJ, Driessen AJM. Tight hydrophobic contacts with the SecB chaperone prevent folding of substrate proteins. Biochemistry 2010; 49:2380-8. [PMID: 20146530 DOI: 10.1021/bi902051e] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The molecular chaperone SecB binds to hydrophobic sections of unfolded secretory proteins and thereby prevents their premature folding prior to secretion by the translocase of Escherichia coli. Here, we have investigated the effect of the single-residue mutation of leucine 42 to arginine (L42R) centrally positioned in the polypeptide binding pocket of SecB on its chaperonin function. The mutant retains its tetrameric structure and SecA targeting function but is defective in its holdase activity. Isothermal titration calorimetry and single-molecule optical tweezer studies suggest that the SecB(L42R) mutant exhibits a reduced polypeptide binding affinity allowing for partial folding of the bound polypeptide chain rendering it translocation-incompetent.
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Affiliation(s)
- Philipp Bechtluft
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and Zernike Institute for Advanced Materials, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands
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12
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Thermodynamics of the protein translocation. Methods Enzymol 2009. [PMID: 21609866 DOI: 10.1016/s0076-6879(09)66012-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Many proteins synthesized in bacteria are secreted from the cytoplasm into the periplasm to function in the cell envelope or in the extracellular medium. The Sec translocase is a primary and evolutionary conserved secretion pathway in bacteria. It catalyzes the translocation of unfolded proteins across the cytoplasmic membrane via the pore-forming SecYEG complex. This process is driven by the proton motive force and ATP hydrolysis facilitated by the SecA motor protein. Current insights in the mechanism of protein translocation are largely based on elaborate multidisciplinary studies performed during the last three decades. To understand the process dynamics, the thermodynamic principles of translocation and the subunit interactions need to be addressed. Isothermal titration calorimetry has been widely applied to study thermodynamics of biological interactions, their stability, and driving forces. Here, we describe the examples that exploit this method to investigate key interactions among components of the Sec translocase and suggest further potential applications of calorimetry.
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13
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Bechtluft P, Nouwen N, Tans SJ, Driessen AJM. SecB--a chaperone dedicated to protein translocation. MOLECULAR BIOSYSTEMS 2009; 6:620-7. [PMID: 20237639 DOI: 10.1039/b915435c] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
SecB is a molecular chaperone in Gram-negative bacteria dedicated to the post-translational translocation of proteins across the cytoplasmic membrane. The entire surface of this chaperone is used for both of its native functions in protein targeting and unfolding. Single molecule studies revealed how SecB affects the folding pathway of proteins and how it prevents the tertiary structure formation and aggregation to support protein translocation.
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Affiliation(s)
- Philipp Bechtluft
- Department of Molecular Microbiology, Groningen Biomolecular Sciences and Biotechnology Institute and the Zernike Institute for Advanced Materials, University of Groningen, Kerklaan 30, 9751 NN Haren, The Netherlands.
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