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Miton CM, Tokuriki N. Insertions and Deletions (Indels): A Missing Piece of the Protein Engineering Jigsaw. Biochemistry 2023; 62:148-157. [PMID: 35830609 DOI: 10.1021/acs.biochem.2c00188] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Over the years, protein engineers have studied nature and borrowed its tricks to accelerate protein evolution in the test tube. While there have been considerable advances, our ability to generate new proteins in the laboratory is seemingly limited. One explanation for these shortcomings may be that insertions and deletions (indels), which frequently arise in nature, are largely overlooked during protein engineering campaigns. The profound effect of indels on protein structures, by way of drastic backbone alterations, could be perceived as "saltation" events that bring about significant phenotypic changes in a single mutational step. Should we leverage these effects to accelerate protein engineering and gain access to unexplored regions of adaptive landscapes? In this Perspective, we describe the role played by indels in the functional diversification of proteins in nature and discuss their untapped potential for protein engineering, despite their often-destabilizing nature. We hope to spark a renewed interest in indels, emphasizing that their wider study and use may prove insightful and shape the future of protein engineering by unlocking unique functional changes that substitutions alone could never achieve.
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Affiliation(s)
- Charlotte M Miton
- Michael Smith Laboratories, University of British Columbia, Vancouver, V6T 1Z4 BC, Canada
| | - Nobuhiko Tokuriki
- Michael Smith Laboratories, University of British Columbia, Vancouver, V6T 1Z4 BC, Canada
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Hoque MA, Zhang Y, Li Z, Cui L, Feng Y. Remodeling enzyme active sites by stepwise loop insertion. Methods Enzymol 2020; 643:111-127. [PMID: 32896277 DOI: 10.1016/bs.mie.2020.07.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The remolding active site loops via residue insertion/deletion as well as substitution is thought to play a key role in enzyme divergent evolution. However, enzyme engineering by residue insertion in active site loops often severely perturbs the protein structural integrity and causes protein misfolding and activity loss. We have designed a stepwise loop insertion strategy (StLois), in which a pair of randomized residues is introduced in a stepwise manner, efficiently collating mutational fitness effects. The strategy of StLois constitutes three key steps. First, the target regions should be identified through structural and functional analysis on the counterpart enzymes. Second, pair residues can be introduced in loop regions through insertion with NNK codon degeneracy. Third, the best hit used as a template for the next round mutagenesis. The residue insertion process can repeat as many times as necessary. By using the StLois method, we have evolved the substrate preference of a lactonase to phosphotriesterase. In this chapter, we describe the detailed StLois technique, which efficiently expands the residue in the loop region and remolds the architecture of enzyme active site for novel catalytic properties.
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Affiliation(s)
- Md Anarul Hoque
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Yong Zhang
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Zhi Li
- Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore
| | - Li Cui
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
| | - Yan Feng
- State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China.
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Emond S, Petek M, Kay EJ, Heames B, Devenish SRA, Tokuriki N, Hollfelder F. Accessing unexplored regions of sequence space in directed enzyme evolution via insertion/deletion mutagenesis. Nat Commun 2020; 11:3469. [PMID: 32651386 PMCID: PMC7351745 DOI: 10.1038/s41467-020-17061-3] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 06/01/2020] [Indexed: 11/22/2022] Open
Abstract
Insertions and deletions (InDels) are frequently observed in natural protein evolution, yet their potential remains untapped in laboratory evolution. Here we introduce a transposon-based mutagenesis approach (TRIAD) to generate libraries of random variants with short in-frame InDels, and screen TRIAD libraries to evolve a promiscuous arylesterase activity in a phosphotriesterase. The evolution exhibits features that differ from previous point mutagenesis campaigns: while the average activity of TRIAD variants is more compromised, a larger proportion has successfully adapted for the activity. Different functional profiles emerge: (i) both strong and weak trade-off between activities are observed; (ii) trade-off is more severe (20- to 35-fold increased kcat/KM in arylesterase with 60-400-fold decreases in phosphotriesterase activity) and (iii) improvements are present in kcat rather than just in KM, suggesting adaptive solutions. These distinct features make TRIAD an alternative to widely used point mutagenesis, accessing functional innovations and traversing unexplored fitness landscape regions.
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Affiliation(s)
- Stephane Emond
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK.
- Evonetix Ltd, Coldhams Business Park, Norman Way, Cambridge, CB1 3LH, UK.
| | - Maya Petek
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK
| | - Emily J Kay
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK
- Cancer Research UK Beatson Institute, Glasgow, G61 1BD, UK
| | - Brennen Heames
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK
- Institute for Evolution and Biodiversity, Westfälische Wilhelms-Universität, Hüfferstrasse 1, 48149, Münster, Germany
| | - Sean R A Devenish
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK
- Fluidic Analytics, The Paddocks Business Centre, Cherry Hinton Road, Cambridge, CB1 8DH, UK
| | - Nobuhiko Tokuriki
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Florian Hollfelder
- Department of Biochemistry, University of Cambridge, Cambridge, CB2 1GA, UK.
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Goldsmith M, Tawfik DS. Enzyme engineering: reaching the maximal catalytic efficiency peak. Curr Opin Struct Biol 2017; 47:140-150. [PMID: 29035814 DOI: 10.1016/j.sbi.2017.09.002] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Revised: 07/04/2017] [Accepted: 09/20/2017] [Indexed: 01/01/2023]
Abstract
The practical need for highly efficient enzymes presents new challenges in enzyme engineering, in particular, the need to improve catalytic turnover (kcat) or efficiency (kcat/KM) by several orders of magnitude. However, optimizing catalysis demands navigation through complex and rugged fitness landscapes, with optimization trajectories often leading to strong diminishing returns and dead-ends. When no further improvements are observed in library screens or selections, it remains unclear whether the maximal catalytic efficiency of the enzyme (the catalytic 'fitness peak') has been reached; or perhaps, an alternative combination of mutations exists that could yield additional improvements. Here, we discuss fundamental aspects of the process of catalytic optimization, and offer practical solutions with respect to overcoming optimization plateaus.
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Affiliation(s)
- Moshe Goldsmith
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel.
| | - Dan S Tawfik
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
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In-frame amber stop codon replacement mutagenesis for the directed evolution of proteins containing non-canonical amino acids: identification of residues open to bio-orthogonal modification. PLoS One 2015; 10:e0127504. [PMID: 26011713 PMCID: PMC4444182 DOI: 10.1371/journal.pone.0127504] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 04/13/2015] [Indexed: 11/19/2022] Open
Abstract
Expanded genetic code approaches are a powerful means to add new and useful chemistry to proteins at defined residues positions. One such use is the introduction of non-biological reactive chemical handles for site-specific biocompatible orthogonal conjugation of proteins. Due to our currently limited information on the impact of non-canonical amino acids (nAAs) on the protein structure-function relationship, rational protein engineering is a “hit and miss” approach to selecting suitable sites. Furthermore, dogma suggests surface exposed native residues should be the primary focus for introducing new conjugation chemistry. Here we describe a directed evolution approach to introduce and select for in-frame codon replacement to facilitate engineering proteins with nAAs. To demonstrate the approach, the commonly reprogrammed amber stop codon (TAG) was randomly introduced in-frame in two different proteins: the bionanotechnologically important cyt b562 and therapeutic protein KGF. The target protein is linked at the gene level to sfGFP via a TEV protease site. In absence of a nAA, an in-frame TAG will terminate translation resulting in a non-fluorescent cell phenotype. In the presence of a nAA, TAG will encode for nAA incorporation so instilling a green fluorescence phenotype on E. coli. The presence of endogenously expressed TEV proteases separates in vivo target protein from its fusion to sfGFP if expressed as a soluble fusion product. Using this approach, we incorporated an azide reactive handle and identified residue positions amenable to conjugation with a fluorescence dye via strain-promoted azide-alkyne cycloaddition (SPAAC). Interestingly, best positions for efficient conjugation via SPAAC were residues whose native side chain were buried through analysis of their determined 3D structures and thus may not have been chosen through rational protein engineering. Molecular modeling suggests these buried native residues could become partially exposed on substitution to the azide containing nAA.
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Currin A, Swainston N, Day PJ, Kell DB. Synthetic biology for the directed evolution of protein biocatalysts: navigating sequence space intelligently. Chem Soc Rev 2015; 44:1172-239. [PMID: 25503938 PMCID: PMC4349129 DOI: 10.1039/c4cs00351a] [Citation(s) in RCA: 251] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Indexed: 12/21/2022]
Abstract
The amino acid sequence of a protein affects both its structure and its function. Thus, the ability to modify the sequence, and hence the structure and activity, of individual proteins in a systematic way, opens up many opportunities, both scientifically and (as we focus on here) for exploitation in biocatalysis. Modern methods of synthetic biology, whereby increasingly large sequences of DNA can be synthesised de novo, allow an unprecedented ability to engineer proteins with novel functions. However, the number of possible proteins is far too large to test individually, so we need means for navigating the 'search space' of possible protein sequences efficiently and reliably in order to find desirable activities and other properties. Enzymologists distinguish binding (Kd) and catalytic (kcat) steps. In a similar way, judicious strategies have blended design (for binding, specificity and active site modelling) with the more empirical methods of classical directed evolution (DE) for improving kcat (where natural evolution rarely seeks the highest values), especially with regard to residues distant from the active site and where the functional linkages underpinning enzyme dynamics are both unknown and hard to predict. Epistasis (where the 'best' amino acid at one site depends on that or those at others) is a notable feature of directed evolution. The aim of this review is to highlight some of the approaches that are being developed to allow us to use directed evolution to improve enzyme properties, often dramatically. We note that directed evolution differs in a number of ways from natural evolution, including in particular the available mechanisms and the likely selection pressures. Thus, we stress the opportunities afforded by techniques that enable one to map sequence to (structure and) activity in silico, as an effective means of modelling and exploring protein landscapes. Because known landscapes may be assessed and reasoned about as a whole, simultaneously, this offers opportunities for protein improvement not readily available to natural evolution on rapid timescales. Intelligent landscape navigation, informed by sequence-activity relationships and coupled to the emerging methods of synthetic biology, offers scope for the development of novel biocatalysts that are both highly active and robust.
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Affiliation(s)
- Andrew Currin
- Manchester Institute of Biotechnology , The University of Manchester , 131, Princess St , Manchester M1 7DN , UK . ; http://dbkgroup.org/; @dbkell ; Tel: +44 (0)161 306 4492
- School of Chemistry , The University of Manchester , Manchester M13 9PL , UK
- Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM) , The University of Manchester , 131, Princess St , Manchester M1 7DN , UK
| | - Neil Swainston
- Manchester Institute of Biotechnology , The University of Manchester , 131, Princess St , Manchester M1 7DN , UK . ; http://dbkgroup.org/; @dbkell ; Tel: +44 (0)161 306 4492
- Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM) , The University of Manchester , 131, Princess St , Manchester M1 7DN , UK
- School of Computer Science , The University of Manchester , Manchester M13 9PL , UK
| | - Philip J. Day
- Manchester Institute of Biotechnology , The University of Manchester , 131, Princess St , Manchester M1 7DN , UK . ; http://dbkgroup.org/; @dbkell ; Tel: +44 (0)161 306 4492
- Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM) , The University of Manchester , 131, Princess St , Manchester M1 7DN , UK
- Faculty of Medical and Human Sciences , The University of Manchester , Manchester M13 9PT , UK
| | - Douglas B. Kell
- Manchester Institute of Biotechnology , The University of Manchester , 131, Princess St , Manchester M1 7DN , UK . ; http://dbkgroup.org/; @dbkell ; Tel: +44 (0)161 306 4492
- School of Chemistry , The University of Manchester , Manchester M13 9PL , UK
- Centre for Synthetic Biology of Fine and Speciality Chemicals (SYNBIOCHEM) , The University of Manchester , 131, Princess St , Manchester M1 7DN , UK
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