1
|
Cohen AA, Keeffe JR, Schiepers A, Dross SE, Greaney AJ, Rorick AV, Gao H, Gnanapragasam PN, Fan C, West AP, Ramsingh AI, Erasmus JH, Pata JD, Muramatsu H, Pardi N, Lin PJ, Baxter S, Cruz R, Quintanar-Audelo M, Robb E, Serrano-Amatriain C, Magneschi L, Fotheringham IG, Fuller DH, Victora GD, Bjorkman PJ. Mosaic sarbecovirus vaccination elicits cross-reactive responses in pre-immunized animals. bioRxiv 2024:2024.02.08.576722. [PMID: 38370696 PMCID: PMC10871317 DOI: 10.1101/2024.02.08.576722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Immunization with mosaic-8b [60-mer nanoparticles presenting 8 SARS-like betacoronavirus (sarbecovirus) receptor-binding domains (RBDs)] elicits more broadly cross-reactive antibodies than homotypic SARS-CoV-2 RBD-only nanoparticles and protects against sarbecoviruses. To investigate original antigenic sin (OAS) effects on mosaic-8b efficacy, we evaluated effects of prior COVID-19 vaccinations in non-human primates and mice on sarbecovirus response breadths elicited by mosaic-8b, admix-8b (8 homotypics), and homotypic SARS-CoV-2, finding greatest cross-reactivity for mosaic-8b. As demonstrated by molecular fate-mapping in which antibodies derived from specific cohorts of B cells are differentially detected, B cells primed by WA1 spike mRNA-LNP dominated antibody responses after RBD-nanoparticle boosting. While mosaic-8b- and homotypic-nanoparticles boosted cross-reactive antibodies, de novo antibodies were predominantly induced with mosaic-8b boosting, and these were specific for variant RBDs with increased identity to RBDs on mosaic-8b. These results inform OAS mechanisms and support using mosaic-8b to protect COVID-19 vaccinated/infected humans against as-yet-unknown SARS-CoV-2 variants and animal sarbecoviruses with human spillover potential.
Collapse
Affiliation(s)
- Alexander A. Cohen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- These authors contributed equally
| | - Jennifer R. Keeffe
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- These authors contributed equally
| | - Ariën Schiepers
- Laboratory of Lymphocyte Dynamics, The Rockefeller University, New York, NY, 10065, USA
| | - Sandra E. Dross
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
- National Primate Research Center, Seattle, WA 98121, USA
| | - Allison J. Greaney
- Medical Scientist Training Program, University of Washington, Seattle, WA 98195, USA
| | - Annie V. Rorick
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Han Gao
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | | | - Chengcheng Fan
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Anthony P. West
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | | | | | - Janice D. Pata
- Wadsworth Center, New York State Department of Health and Department of Biomedical Sciences, University at Albany, Albany, NY, 12201, USA
| | - Hiromi Muramatsu
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Norbert Pardi
- Department of Microbiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | | | - Scott Baxter
- Ingenza Ltd, Roslin Innovation Centre, Charnock Bradley Building, Roslin, EH25 9RG, UK
| | - Rita Cruz
- Ingenza Ltd, Roslin Innovation Centre, Charnock Bradley Building, Roslin, EH25 9RG, UK
| | - Martina Quintanar-Audelo
- Ingenza Ltd, Roslin Innovation Centre, Charnock Bradley Building, Roslin, EH25 9RG, UK
- Present address: Centre for Inflammation Research and Institute of Regeneration and Repair, The University of Edinburgh, Edinburgh, EH16 4UU, UK
| | - Ellis Robb
- Ingenza Ltd, Roslin Innovation Centre, Charnock Bradley Building, Roslin, EH25 9RG, UK
| | | | - Leonardo Magneschi
- Ingenza Ltd, Roslin Innovation Centre, Charnock Bradley Building, Roslin, EH25 9RG, UK
| | - Ian G. Fotheringham
- Ingenza Ltd, Roslin Innovation Centre, Charnock Bradley Building, Roslin, EH25 9RG, UK
| | - Deborah H. Fuller
- Department of Microbiology, University of Washington, Seattle, WA 98195, USA
- National Primate Research Center, Seattle, WA 98121, USA
| | - Gabriel D. Victora
- Laboratory of Lymphocyte Dynamics, The Rockefeller University, New York, NY, 10065, USA
| | - Pamela J. Bjorkman
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Lead contact
| |
Collapse
|
2
|
Kjeldsen A, Kay JE, Baxter S, McColm S, Serrano‐Amatriain C, Parker S, Robb E, Arnold SA, Gilmour C, Raper A, Robertson G, Fleming R, Smith BO, Fotheringham IG, Christie JM, Magneschi L. The fluorescent protein iLOV as a reporter for screening of high‐yield production of antimicrobial peptides in
Pichia pastoris. Microb Biotechnol 2022; 15:2126-2139. [PMID: 35312165 PMCID: PMC9249318 DOI: 10.1111/1751-7915.14034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 03/03/2022] [Accepted: 03/05/2022] [Indexed: 11/28/2022] Open
Abstract
The methylotrophic yeast Pichia pastoris is commonly used for the production of recombinant proteins at scale. The identification of an optimally overexpressing strain following transformation can be time and reagent consuming. Fluorescent reporters like GFP have been used to assist identification of superior producers, but their relatively big size, maturation requirements and narrow temperature range restrict their applications. Here, we introduce the use of iLOV, a flavin‐based fluorescent protein, as a fluorescent marker to identify P. pastoris high‐yielding strains easily and rapidly. The use of this fluorescent protein as a fusion partner is exemplified by the production of the antimicrobial peptide NI01, a difficult target to overexpress in its native form. iLOV fluorescence correlated well with protein expression level and copy number of the chromosomally integrated gene. An easy and simple medium‐throughput plate‐based screen directly following transformation is demonstrated for low complexity screening, while a high‐throughput method using fluorescence‐activated cell sorting (FACS) allowed for comprehensive library screening. Both codon optimization of the iLOV_NI01 fusion cassettes and different integration strategies into the P. pastoris genome were tested to produce and isolate a high‐yielding strain. Checking the genetic stability, process reproducibility and following the purification of the active native peptide are eased by visualization of and efficient cleavage from the iLOV reporter. We show that this system can be used for expression and screening of several different antimicrobial peptides recombinantly produced in P. pastoris.
Collapse
Affiliation(s)
- Annemette Kjeldsen
- Ingenza Ltd Roslin Innovation Centre Charnock Bradley Building Roslin EH25 9RG UK
- Institute of Molecular, Cell and Systems Biology College of Medical, Veterinary and Life Sciences University of Glasgow Bower Building Glasgow G12 8QQ UK
| | - Jack E. Kay
- Ingenza Ltd Roslin Innovation Centre Charnock Bradley Building Roslin EH25 9RG UK
| | - Scott Baxter
- Ingenza Ltd Roslin Innovation Centre Charnock Bradley Building Roslin EH25 9RG UK
| | - Stephen McColm
- Ingenza Ltd Roslin Innovation Centre Charnock Bradley Building Roslin EH25 9RG UK
| | | | - Scott Parker
- Ingenza Ltd Roslin Innovation Centre Charnock Bradley Building Roslin EH25 9RG UK
| | - Ellis Robb
- Ingenza Ltd Roslin Innovation Centre Charnock Bradley Building Roslin EH25 9RG UK
| | - S. Alison Arnold
- Ingenza Ltd Roslin Innovation Centre Charnock Bradley Building Roslin EH25 9RG UK
| | - Craig Gilmour
- Ingenza Ltd Roslin Innovation Centre Charnock Bradley Building Roslin EH25 9RG UK
| | - Anna Raper
- The Roslin Institute & Royal (Dick) School of Veterinary Studies University of Edinburgh Easter Bush Midlothian EH25 9RG UK
| | - Graeme Robertson
- The Roslin Institute & Royal (Dick) School of Veterinary Studies University of Edinburgh Easter Bush Midlothian EH25 9RG UK
| | - Robert Fleming
- The Roslin Institute & Royal (Dick) School of Veterinary Studies University of Edinburgh Easter Bush Midlothian EH25 9RG UK
| | - Brian O. Smith
- Institute of Molecular, Cell and Systems Biology College of Medical, Veterinary and Life Sciences University of Glasgow Bower Building Glasgow G12 8QQ UK
| | - Ian G. Fotheringham
- Ingenza Ltd Roslin Innovation Centre Charnock Bradley Building Roslin EH25 9RG UK
| | - John M. Christie
- Institute of Molecular, Cell and Systems Biology College of Medical, Veterinary and Life Sciences University of Glasgow Bower Building Glasgow G12 8QQ UK
| | - Leonardo Magneschi
- Ingenza Ltd Roslin Innovation Centre Charnock Bradley Building Roslin EH25 9RG UK
| |
Collapse
|
3
|
Baxter S, Royer S, Grogan G, Brown F, Holt-Tiffin KE, Taylor IN, Fotheringham IG, Campopiano DJ. An Improved Racemase/Acylase Biotransformation for the Preparation of Enantiomerically Pure Amino Acids. J Am Chem Soc 2012; 134:19310-3. [DOI: 10.1021/ja305438y] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Scott Baxter
- The EastChem School of Chemistry,
Joseph Black Building, The University of Edinburgh, Edinburgh, EH9
3JJ, U.K
| | - Sylvain Royer
- Department of
Biology and Biochemistry,
University of Bath, Bath, BA2 7AY, U.K
| | - Gideon Grogan
- York Structural Biology Laboratory,
Department of Chemistry, University of York, York, YO10 5DD, U.K
| | - Fraser Brown
- Ingenza Ltd,Wallace
Building,
Roslin Biocentre, Roslin, EH25 9PP, U.K
| | - Karen E. Holt-Tiffin
- Chirotech Technology Centre,
Dr. Reddy’s Laboratories Ltd, 410 Cambridge Science Park, Cambridge,
CB4 0PE, U.K
| | - Ian N. Taylor
- Chirotech Technology Centre,
Dr. Reddy’s Laboratories Ltd, 410 Cambridge Science Park, Cambridge,
CB4 0PE, U.K
| | | | - Dominic J. Campopiano
- The EastChem School of Chemistry,
Joseph Black Building, The University of Edinburgh, Edinburgh, EH9
3JJ, U.K
| |
Collapse
|
4
|
Enright A, Alexandre FR, Roff G, Fotheringham IG, Dawson MJ, Turner NJ. Stereoinversion of β- and γ-substituted α-amino acids using a chemo-enzymatic oxidation–reduction procedure. Chem Commun (Camb) 2003:2636-7. [PMID: 14594318 DOI: 10.1039/b309787k] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Both D- and L-beta- and gamma-substituted alpha-amino acids can be interconverted to their respective L- and D- diastereoisomers by treatment with an enantioselective amino acid oxidase and a chemical reducing agent.
Collapse
Affiliation(s)
- Alexis Enright
- School of Chemistry, The University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, UK EH9 3JJ
| | | | | | | | | | | |
Collapse
|
5
|
Affiliation(s)
- Tao Li
- Great Lakes Fine Chemicals, 601 East Kensington Rd, Mt. Prospect, Illinois 60056, U.S.A
| | - Anna B. Kootstra
- Great Lakes Fine Chemicals, 601 East Kensington Rd, Mt. Prospect, Illinois 60056, U.S.A
| | - Ian G. Fotheringham
- Great Lakes Fine Chemicals, 601 East Kensington Rd, Mt. Prospect, Illinois 60056, U.S.A
| |
Collapse
|
6
|
Alexandre FR, Pantaleone DP, Taylor PP, Fotheringham IG, Ager DJ, Turner NJ. Amine–boranes: effective reducing agents for the deracemisation of dl-amino acids using l-amino acid oxidase from Proteus myxofaciens. Tetrahedron Lett 2002. [DOI: 10.1016/s0040-4039(01)02233-x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
|
7
|
Ager DJ, Fotheringham IG. Methods for the synthesis of unnatural amino acids. Curr Opin Drug Discov Devel 2001; 4:800-7. [PMID: 11899620] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
A wide variety of methods have been used to prepare unnatural amino acids. This review covers methods reported between 2000 and the early part of 2001. Some of the approaches discussed are applications of established methods, but emphasis has been given to new approaches that could be generally applicable to large-scale syntheses, including catalytic reactions such as the Strecker reaction and biological approaches.
Collapse
Affiliation(s)
- D J Ager
- RCCorp, PO BOX 59049, Schaumburg, IL 60195-0049, USA
| | | |
Collapse
|
8
|
Ager DJ, Fotheringham IG, Li T, Pantaleone DP, Senkpeil RF. The large scale synthesis of "unnatural" amino acids. Enantiomer 2000; 5:235-43. [PMID: 11126863] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/15/2023]
Abstract
The introduction of a stereogenic centre to produce an "unnatural" amino acid can be accomplished in a variety of ways ranging from asymmetric hydrogenation to biotransformations based on transaminase enzymes. Our transaminase approach can be used to access a wide variety of L- and D-amino acids from an alpha-keto acid substrate. It is run as a whole cell biotransformation and uses coupled enzyme systems. In addition, formation of amino acids with small side chains, such as 2-aminobutyrate, can cause significant isolation problems due to the presence of small amounts of other amino acids, such as alanine. The improvements we have made to the approach are illustrated with 2-aminobutyrate as the example. Aspartic acid is used as the amino donor and gives rise to the formation of pyruvate, a substrate for the transaminase enzymes. We have now developed an alternative approach where lysine is used as the amino donor to allow formation of a cyclic by-product that is removed from the equilibrium.
Collapse
Affiliation(s)
- D J Ager
- NSC Technologies, A Division of Great Lakes Fine Chemicals, 601 East Kensington Road, Mount Prospect, IL 60056, USA
| | | | | | | | | |
Collapse
|
9
|
Fotheringham IG, Grinter N, Pantaleone DP, Senkpeil RF, Taylor PP. Engineering of a novel biochemical pathway for the biosynthesis of L-2-aminobutyric acid in Escherichia coli K12. Bioorg Med Chem 1999; 7:2209-13. [PMID: 10579528 DOI: 10.1016/s0968-0896(99)00153-4] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
L-2-Aminobutyric acid was synthesised in a transamination reaction from L-threonine and L-aspartic acid as substrates in a whole cell biotransformation using recombinant Escherichia coli K12. The cells contained the cloned genes tyrB, ilvA and alsS which respectively encode tyrosine aminotransferase of E. coli, threonine deaminase of E. coli and alpha-acetolactate synthase of B. subtilis 168. The 2-aminobutyric acid was produced by the action of the aminotransferase on 2-ketobutyrate and L-aspartate. The 2-ketobutyrate is generated in situ from L-threonine by the action of the deaminase, and the pyruvate by-product is eliminated by the acetolactate synthase. The concerted action of the three enzymes offers significant yield and purity advantages over the process using the transaminase alone with an eight to tenfold increase in the ratio of product to the major impurity.
Collapse
|
10
|
Taylor PP, Pantaleone DP, Senkpeil RF, Fotheringham IG. Novel biosynthetic approaches to the production of unnatural amino acids using transaminases. Trends Biotechnol 1998; 16:412-8. [PMID: 9807838 DOI: 10.1016/s0167-7799(98)01240-2] [Citation(s) in RCA: 190] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Transaminase enzymes are being increasingly applied to the large-scale synthesis of unnatural and nonproteinogenic amino acids. Typically displaying relaxed substrate specificity, rapid reaction rates and lacking the need for cofactor regeneration, they possess many characteristics that make them desirable as effective biocatalysts. By judiciously combining the transaminase reaction with additional enzymatic steps, this approach can be used very efficiently to prepare a broad range of D- and L-amino acids.
Collapse
Affiliation(s)
- P P Taylor
- NSC Technologies, Monsanto, Mount Prospect, IL 60056-1300, USA.
| | | | | | | |
Collapse
|
11
|
Fotheringham IG, Bledig SA, Taylor PP. Characterization of the genes encoding D-amino acid transaminase and glutamate racemase, two D-glutamate biosynthetic enzymes of Bacillus sphaericus ATCC 10208. J Bacteriol 1998; 180:4319-23. [PMID: 9696787 PMCID: PMC107435 DOI: 10.1128/jb.180.16.4319-4323.1998] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Bacillus sphaericus and other Bacillus spp., D-amino acid transaminase has been considered solely responsible for biosynthesis of D-glutamate, an essential component of cell wall peptidoglycan, in contrast to the glutamate racemase employed by many other bacteria. We report here the cloning of the dat gene encoding D-amino acid transaminase and the glr gene encoding a glutamate racemase from B. sphaericus ATCC 10208. The glr gene encodes a 28. 8-kDa protein with 40 to 50% sequence identity to the glutamate racemases of Lactobacillus, Pediococcus, and Staphylococcus species. The dat gene encodes a 31.4-kDa peptide with 67% primary sequence homology to the D-amino acid transaminase of the thermophilic Bacillus sp. strain YM1.
Collapse
Affiliation(s)
- I G Fotheringham
- Biosciences Laboratory, NSC Technologies, Mt. Prospect, Illinois 60056, USA.
| | | | | |
Collapse
|
12
|
Taylor PP, Fotheringham IG. Nucleotide sequence of the Bacillus licheniformis ATCC 10716 dat gene and comparison of the predicted amino acid sequence with those of other bacterial species. Biochim Biophys Acta 1997; 1350:38-40. [PMID: 9003455 DOI: 10.1016/s0167-4781(96)00204-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The gene encoding the D-aminotransferase from Bacillus licheniformis was cloned and the complete DNA sequence was determined. The deduced D-aminotransferase protein sequence, consists of 283 amino acids and shows a high degree of homology with other Bacillus D-aminotransferases, branched chain aminotransferase of Escherichia coli and the 4-amino-benzoate-4-deoxychorismate lyase of Bacillus subtilis and Escherichia coli.
Collapse
Affiliation(s)
- P P Taylor
- Biosciences, NSC Technologies, Mt. Prospect, IL 60056, USA
| | | |
Collapse
|
13
|
Fotheringham IG, Kidman GE, McArthur BS, Robinson LE, Scollar MP. Aminotransferase-catalyzed conversion of D-amino acids to L-amino acids. Biotechnol Prog 1991. [DOI: 10.1021/bp00010a014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
14
|
Fotheringham IG, Dacey SA, Taylor PP, Smith TJ, Hunter MG, Finlay ME, Primrose SB, Parker DM, Edwards RM. The cloning and sequence analysis of the aspC and tyrB genes from Escherichia coli K12. Comparison of the primary structures of the aspartate aminotransferase and aromatic aminotransferase of E. coli with those of the pig aspartate aminotransferase isoenzymes. Biochem J 1986; 234:593-604. [PMID: 3521591 PMCID: PMC1146613 DOI: 10.1042/bj2340593] [Citation(s) in RCA: 95] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
In this paper we describe the cloning and sequence analysis of the tyrB and aspC genes from Escherichia coli K12, which encode the aromatic aminotransferase and aspartate aminotransferase respectively. The tyrB gene was isolated from a cosmid carrying the nearby dnaB gene, identified by its ability to complement a dnaB lesion. Deletion and linker insertion analysis located the tyrB gene to a 1.7-kilobase NruI-HindIII-digest fragment. Sequence analysis revealed a gene encoding a 43 000 Da polypeptide. The gene starts with a GTG codon and is closely followed by a structure resembling a rho independent terminator. The aspC gene was cloned by screening gene banks, prepared from a prototrophic E. coli K12 strain, for plasmids able to complement the aspC tyrB lesions in the aminotransferase-deficient strain HW225. Sub-cloning and deletion analysis located the aspC gene on a 1.8-kilobase HincII-StuI-digest fragment. Sequence analysis revealed the presence of a gene encoding a 43 000 Da protein, the sequence of which is identical with that previously obtained for the aspartate aminotransferase from E. coli B. Considerable overproduction of the two enzymes was demonstrated. We compared the deduced protein sequences with those of the pig mitochondrial and cytoplasmic aspartate aminotransferases. From the extensive homology observed we are able to propose that the two E. coli enzymes possess subunit structures, subunit interactions and coenzyme-binding and substrate-binding sites that are very similar both to each other and to those of the mammalian enzymes and therefore must also have very similar catalytic mechanisms. Comparison of the aspC and tyrB gene sequences reveals that they appear to have diverged as much as is possible within the constraints of functionality and codon usage.
Collapse
|