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Chernyshov SV, Masulis IS, Mikoulinskaia GV. From DNA to lytic proteins: transcription and translation of the bacteriophage T5 holin/endolysin operon. World J Microbiol Biotechnol 2024; 40:256. [PMID: 38926173 DOI: 10.1007/s11274-024-04063-2] [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: 12/27/2023] [Accepted: 06/23/2024] [Indexed: 06/28/2024]
Abstract
The analysis of transcriptional activity of the bacteriophage T5 hol/endo operon conducted in the paper revealed a strong constitutive promoter recognized by E. coli RNA polymerase and a transcription initiation point of the operon. It was also shown that the only translational start codon for holin was a non-canonical TTG. Translation initiation regions (TIRs) of both genes of the operon (hol and endo) were further analyzed using chimeric constructs, in which parts of the hol/endo regulatory regions were fused with the gene of a reporter protein (EGFP). It was found that TIR of hol was 20 times less effective than that of endo. As it turned out, the level of EGFP production was influenced by the composition of the constructs and the type of the hol start codon. Apparently, the translational suppression of holin's accumulation and posttranslational activation of endolysin by Ca2+ are the main factors ensuring the proper timing of the host cell lysis by bacteriophage T5. The approach based on the use of chimeric constructs proposed in the paper can be recommended for studying other native or artificial operons of any complexity: analyzing the impacts of separate DNA regions, as well as their coupled effect, on the processes of transcription and translation of recombinant protein(s).
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Affiliation(s)
- Sergei V Chernyshov
- Branch of Shemyakin & Ovchinnikov's Institute of Bioorganic Chemistry RAS, Prospekt Nauki, 6, Pushchino, Moscow region, Pushchino, Moscow region, 142290, Russia
| | - Irina S Masulis
- Institute of Cell Biophysics RAS PBC RAS, Institutskaya ul., 3, Pushchino, Pushchino, Moscow region, 142290, Russia
| | - Galina V Mikoulinskaia
- Branch of Shemyakin & Ovchinnikov's Institute of Bioorganic Chemistry RAS, Prospekt Nauki, 6, Pushchino, Moscow region, Pushchino, Moscow region, 142290, Russia.
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Liu Q, Sun S, Yang Z, Shao Y, Li X. Serum Amyloid A 4 as a Common Marker of Persistent Inflammation in Patients with Neovascular Age-Related Macular Degeneration and Polypoidal Choroidal Vasculopathy. J Inflamm Res 2023; 16:3783-3797. [PMID: 37663754 PMCID: PMC10474861 DOI: 10.2147/jir.s417791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 08/22/2023] [Indexed: 09/05/2023] Open
Abstract
Background Neovascular age-related macular degeneration (nAMD) and its subtype, polypoidal choroidal vasculopathy (PCV), are common choroidal vasculopathies. Although they share many common clinical manifestations and treatment strategies, a lack of comprehensive analysis of these conditions means that it is difficult for researchers to further explore the common pathomechanisms of nAMD and PCV. The aim of this study was to characterize aqueous humor (AH) proteome alterations and identify a novel biomarker related to both nAMD and PCV. Methods Liquid Chromatography with tandem mass spectrometry (LC-MS/MS) was adopted to analyze the AH proteomes of nAMD, PCV and controls. The target protein was validated using the enzyme-linked immunosorbent assay (ELISA) and subjected to receiver operating characteristic (ROC) curve analysis. Results A total of 737 different proteins were identified in all the groups, of which 544 were quantifiable. The bioinformatics analysis suggested that immune response activation is the essential event in both nAMD and PCV. Serum amyloid A (SAA) 4 is closely associated with a number of chronic inflammatory diseases, and it was enriched as the hub protein. ROC analysis showed that SAA4 could distinguish both nAMD and PCV from the controls. Conclusion This comprehensive study provides insights into, and furthers our understanding of, the pathological mechanism of nAMD and PCV. Additionally, the SAA4 level alteration may serve as a common biomarker of nAMD and PCV.
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Affiliation(s)
- Qingyan Liu
- Tianjin Key Laboratory of Retinal Functions and Diseases, Tianjin Branch of National Clinical Research Center for Ocular Disease, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin, 300384, People’s Republic of China
- Department of Ophthalmology, Anhui NO.2 Provincial People’s hospital, Hefei, 230041, People’s Republic of China
| | - Shuo Sun
- Tianjin Key Laboratory of Retinal Functions and Diseases, Tianjin Branch of National Clinical Research Center for Ocular Disease, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin, 300384, People’s Republic of China
| | - Zhengwei Yang
- Tianjin Key Laboratory of Retinal Functions and Diseases, Tianjin Branch of National Clinical Research Center for Ocular Disease, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin, 300384, People’s Republic of China
| | - Yan Shao
- Tianjin Key Laboratory of Retinal Functions and Diseases, Tianjin Branch of National Clinical Research Center for Ocular Disease, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin, 300384, People’s Republic of China
| | - Xiaorong Li
- Tianjin Key Laboratory of Retinal Functions and Diseases, Tianjin Branch of National Clinical Research Center for Ocular Disease, Eye Institute and School of Optometry, Tianjin Medical University Eye Hospital, Tianjin, 300384, People’s Republic of China
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Fernández JA, Deguchi H, Elias DJ, Griffin JH. Serum amyloid A4 is a procoagulant apolipoprotein that it is elevated in venous thrombosis patients. Res Pract Thromb Haemost 2020; 4:217-223. [PMID: 32110751 PMCID: PMC7040552 DOI: 10.1002/rth2.12291] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Revised: 11/11/2019] [Accepted: 11/14/2019] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Serum amyloid A4 (SAA4) is an apolipoprotein that is in the SAA family and it is constitutively translated. Previously, acute-phase SAA1 and SAA2 levels were associated with venous thromboembolism (VTE). OBJECTIVE We investigated the association of plasma SAA4 with VTE and the role of SAA4 in coagulation. PATIENTS AND METHODS The association of SAA4 with VTE in a case-control study of adult VTE subjects (N = 113 each group) and the effects of recombinant SAA4 on plasma blood coagulation assays and prothrombin activation initiated by factor Xa were evaluated. RESULTS Plasma SAA4 levels in VTE subjects were higher vs. controls (48.1 vs. 38.4 µg/mL; P < .001). Elevated plasma SAA4 level (above the 90th percentile of controls) was associated with increased VTE occurrence (odds ratio, 3.8; 95% confidence interval, 1.8-8.0). This association remained significant after the adjustment for acute-phase SAA level, suggesting that SAA4 associated with VTE is independent of acute-phase SAA. Two isoforms of SAA4, that is, glycosylated and nonglycosylated SAA4 isoforms, were each higher in VTE patients. When recombinant SAA4 was added to plasma, it shortened factor Xa-1-stage clotting times, showing that it enhances clotting in plasma. In reaction mixtures containing purified factors Xa and Va and prothrombin, recombinant SAA4 increased prothrombin activation, showing that it enhances prothrombinase activity. CONCLUSION Elevated plasma constitutive SAA4 levels were linked to VTE in adults, and SAA4 can enhance thrombin generation in plasma. Our data highlight a previously unknown procoagulant activity of SAA4 that appears to be related to risk of venous thrombotic events.
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Affiliation(s)
- José A. Fernández
- Department of Molecular MedicineThe Scripps Research InstituteLa JollaCAUSA
| | - Hiroshi Deguchi
- Department of Molecular MedicineThe Scripps Research InstituteLa JollaCAUSA
| | - Darlene J. Elias
- Department of Molecular MedicineThe Scripps Research InstituteLa JollaCAUSA
| | - John H. Griffin
- Department of Molecular MedicineThe Scripps Research InstituteLa JollaCAUSA
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Rossmann C, Windpassinger C, Brunner D, Kovacevic A, Schweighofer N, Malli R, Schuligoi R, Prokesch A, Kluve-Beckerman B, Graier WF, Kratky D, Sattler W, Malle E. Characterization of rat serum amyloid A4 (SAA4): a novel member of the SAA superfamily. Biochem Biophys Res Commun 2014; 450:1643-9. [PMID: 25044109 PMCID: PMC4145149 DOI: 10.1016/j.bbrc.2014.07.054] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 07/11/2014] [Indexed: 11/16/2022]
Abstract
The full length rat SAA4 (rSAA4) mRNA was characterized by rapid amplification of cDNA ends. rSAA4 mRNA has 1830 bases including a GA dinucleotide tandem repeat in the 5′UTR. Three consecutive C/EBP promoter elements are crucial for transcription of rSAA4. rSAA4 is abundantly expressed in the liver on mRNA and protein level.
The serum amyloid A (SAA) family of proteins is encoded by multiple genes, which display allelic variation and a high degree of homology in mammals. The SAA1/2 genes code for non-glycosylated acute-phase SAA1/2 proteins, that may increase up to 1000-fold during inflammation. The SAA4 gene, well characterized in humans (hSAA4) and mice (mSaa4) codes for a SAA4 protein that is glycosylated only in humans. We here report on a previously uncharacterized SAA4 gene (rSAA4) and its product in Rattus norvegicus, the only mammalian species known not to express acute-phase SAA. The exon/intron organization of rSAA4 is similar to that reported for hSAA4 and mSaa4. By performing 5′- and 3′RACE, we identified a 1830-bases containing rSAA4 mRNA (including a GA-dinucleotide tandem repeat). Highest rSAA4 mRNA expression was detected in rat liver. In McA-RH7777 rat hepatoma cells, rSAA4 transcription was significantly upregulated in response to LPS and IL-6 while IL-1α/β and TNFα were without effect. Luciferase assays with promoter-truncation constructs identified three proximal C/EBP-elements that mediate expression of rSAA4 in McA-RH7777 cells. In line with sequence prediction a 14-kDa non-glycosylated SAA4 protein is abundantly expressed in rat liver. Fluorescence microscopy revealed predominant localization of rSAA4-GFP-tagged fusion protein in the ER.
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Affiliation(s)
- Christine Rossmann
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | | | - Daniela Brunner
- Institute of Human Genetics, Medical University of Graz, Graz, Austria
| | - Alenka Kovacevic
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Natascha Schweighofer
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Roland Malli
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Rufina Schuligoi
- Institute of Experimental and Clinical Pharmacology, Medical University of Graz, Graz, Austria
| | - Andreas Prokesch
- Institute of Cell Biology, Histology and Embryology, Medical University of Graz, Graz, Austria; Institute of Biochemistry, Graz University of Technology, Graz, Austria
| | - Barbara Kluve-Beckerman
- Department of Pathology and Laboratory Medicine, Indiana University School of Medicine, Indianapolis, IN, USA
| | - Wolfgang F Graier
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Dagmar Kratky
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Wolfgang Sattler
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria
| | - Ernst Malle
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
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Rossmann C, Hammer A, Koyani CN, Kovacevic A, Siwetz M, Desoye G, Poehlmann TG, Markert UR, Huppertz B, Sattler W, Malle E. Expression of serum amyloid A4 in human trophoblast-like choriocarcinoma cell lines and human first trimester/term trophoblast cells. Placenta 2014; 35:661-4. [PMID: 24951172 PMCID: PMC4119475 DOI: 10.1016/j.placenta.2014.05.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Revised: 05/27/2014] [Accepted: 05/29/2014] [Indexed: 11/16/2022]
Abstract
Trophoblast invasion into uterine tissues represents a hallmark of first trimester placental development. As expression of serum amyloid A4 (SAA4) occurs in tumorigenic and invasive tissues we here investigated whether SAA4 is present in trophoblast-like human AC1-M59/Jeg-3 cells and trophoblast preparations of human first trimester and term placenta. SAA4 mRNA was expressed in non-stimulated and cytokine-treated AC1-M59/Jeg-3 cells. In purified trophoblast cells SAA4 mRNA expression was upregulated at weeks 10 and 12 of pregnancy. Western-blot and immunohistochemical staining of first trimester placental tissue revealed pronounced SAA4 expression in invasive trophoblast cells indicating a potential role of SAA4 during invasion. SAA4 mRNA is expressed in Jeg-3 and AC1-M59 cells. SAA4 mRNA is expressed in first trimester/term trophoblast cells. SAA4 mRNA is upregulated at pregnancy week 10 and 12. SAA4 protein is present in interstitial, intramural and intraluminal trophoblast cells.
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Affiliation(s)
- C Rossmann
- Medical University of Graz, Institute of Molecular Biology and Biochemistry, Graz A-8010, Austria
| | - A Hammer
- Medical University of Graz, Institute of Cell Biology, Histology and Embryology, Graz, Austria
| | - C N Koyani
- Medical University of Graz, Institute of Molecular Biology and Biochemistry, Graz A-8010, Austria
| | - A Kovacevic
- Medical University of Graz, Institute of Molecular Biology and Biochemistry, Graz A-8010, Austria
| | - M Siwetz
- Medical University of Graz, Institute of Cell Biology, Histology and Embryology, Graz, Austria
| | - G Desoye
- Medical University of Graz, Department of Obstetrics and Gynecology, Graz, Austria
| | - T G Poehlmann
- Placenta-Laboratory, Department of Obstetrics, University Hospital Jena, Jena, Germany
| | - U R Markert
- Placenta-Laboratory, Department of Obstetrics, University Hospital Jena, Jena, Germany
| | - B Huppertz
- Medical University of Graz, Institute of Cell Biology, Histology and Embryology, Graz, Austria
| | - W Sattler
- Medical University of Graz, Institute of Molecular Biology and Biochemistry, Graz A-8010, Austria
| | - E Malle
- Medical University of Graz, Institute of Molecular Biology and Biochemistry, Graz A-8010, Austria.
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Sarilla S, Habib SY, Tollefsen DM, Friedman DB, Arnett DR, Verhamme IM. Glycosaminoglycan-binding properties and kinetic characterization of human heparin cofactor II expressed in Escherichia coli. Anal Biochem 2010; 406:166-75. [PMID: 20670608 DOI: 10.1016/j.ab.2010.07.024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2010] [Revised: 07/21/2010] [Accepted: 07/22/2010] [Indexed: 10/19/2022]
Abstract
Irreversible inactivation of alpha-thrombin (T) by the serpin, heparin cofactor II (HCII), is accelerated by ternary complex formation with the glycosaminoglycans (GAGs) heparin and dermatan sulfate (DS). Low expression of human HCII in Escherichia coli was optimized by silent mutation of 27 rare codons and five secondary Shine-Dalgarno sequences in the cDNA. The inhibitory activities of recombinant HCII, and native and deglycosylated plasma HCII, and their affinities for heparin and DS were compared. Recombinant and deglycosylated HCII bound heparin with dissociation constants (K(D)) of 6+/-1 and 7+/-1 microM, respectively, approximately 6-fold tighter than plasma HCII, with K(D) 40+/-4 microM. Binding of recombinant and deglycosylated HCII to DS, both with K(D) 4+/-1 microM, was approximately 4-fold tighter than for plasma HCII, with K(D) 15+/-4 microM. Recombinant HCII, lacking N-glycosylation and tyrosine sulfation, inactivated alpha-thrombin with a 1:1 stoichiometry, similar to plasma HCII. Second-order rate constants for thrombin inactivation by recombinant and deglycosylated HCII were comparable, at optimal GAG concentrations that were lower than those for plasma HCII, consistent with its weaker GAG binding. This weaker binding may be attributed to interference of the Asn(169)N-glycan with the HCII heparin-binding site.
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Affiliation(s)
- Suryakala Sarilla
- Department of Pathology, Vanderbilt University School of Medicine, C3321A Medical Center North, Nashville, TN 37232, USA
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Kovacevic A, Hammer A, Stadelmeyer E, Windischhofer W, Sundl M, Ray A, Schweighofer N, Friedl G, Windhager R, Sattler W, Malle E. Expression of serum amyloid A transcripts in human bone tissues, differentiated osteoblast-like stem cells and human osteosarcoma cell lines. J Cell Biochem 2008; 103:994-1004. [PMID: 17849429 PMCID: PMC4861207 DOI: 10.1002/jcb.21472] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Although the liver is the primary site of cytokine-mediated expression of acute-phase serum amyloid A (SAA) protein, extrahepatic production has also been reported. Besides its role in amyloidosis and lipid homeostasis during the acute-phase, SAA has recently been assumed to contribute to bone and cartilage destruction. However, expression of SAA in human osteogenic tissue has not been studied. Therefore, we first show that SAA1 (coding for the major SAA isoform) but not SAA2 transcripts are expressed in human trabecular and cortical bone fractions and bone marrow. Next, we show expression of (i) IL-1, IL-6, and TNF receptor transcripts; (ii) the human homolog of SAA-activating factor-1 (SAF-1, a transcription factor involved in cytokine-mediated induction of SAA genes); and (iii) SAA1/2 transcripts in non-differentiated and, to a higher extent, in osteoblast-like differentiated human mesenchymal stem cells. Third, we provide evidence that human osteoblast-like cells of tumor origin (MG-63 and SAOS-2) express SAF-1 under basal conditions. SAA1/2 transcripts are expressed under basal conditions (SAOS-2) and cytokine-mediated conditions (MG-63 and SAOS-2). RT-PCR, Western blot analysis, and immunofluorescence technique confirmed cytokine-mediated expression of SAA on RNA and protein level in osteosarcoma cell lines while SAA4, a protein of unknown function, is constitutively expressed in all osteogenic tissues investigated.
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Affiliation(s)
- Alenka Kovacevic
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Center of Molecular Medicine, Graz, Austria
| | - Astrid Hammer
- Institute of Cell Biology, Histology and Embryology, Center of Molecular Medicine, Medical University of Graz, Center of Molecular Medicine, Graz, Austria
| | - Elke Stadelmeyer
- Department of Orthopaedics, Graz University Hospital, Medical University of Graz, Graz, Austria
| | - Werner Windischhofer
- Department of Pediatrics, Research Unit of Osteological Research and Analytical Mass Spectrometry, Medical University of Graz, Graz, Austria
| | - Monika Sundl
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Center of Molecular Medicine, Graz, Austria
| | - Alpana Ray
- Department of Veterinary Pathobiology, University of Missouri-Columbia, Columbia, MO 65211
| | - Natascha Schweighofer
- Division of Endocrinology and Nuclear Medicine, Department of Internal Medicine, Medical University of Graz, Graz, Austria
| | - Gerald Friedl
- Department of Orthopaedics, Graz University Hospital, Medical University of Graz, Graz, Austria
| | - Reinhard Windhager
- Department of Orthopaedics, Graz University Hospital, Medical University of Graz, Graz, Austria
| | - Wolfgang Sattler
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Center of Molecular Medicine, Graz, Austria
| | - Ernst Malle
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Center of Molecular Medicine, Graz, Austria
- Correspondence to: Ernst Malle, Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, A-8010 Graz, Austria.
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Bandmann N, Nygren PÅ. Combinatorial expression vector engineering for tuning of recombinant protein production in Escherichia coli. Nucleic Acids Res 2007; 35:e32. [PMID: 17264122 PMCID: PMC1865067 DOI: 10.1093/nar/gkl1171] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The complex and integrated nature of both genetic and protein level factors influencing recombinant protein production in Escherichia coli makes it difficult to predict the optimal expression strategy for a given protein. Here, two combinatorial library strategies were evaluated for their capability of tuning recombinant protein production in the cytoplasm of E. coli. Large expression vector libraries were constructed through either conservative (ExLib1) or free (ExLib2) randomization of a seven-amino-acid window strategically located between a degenerated start codon and a sequence encoding a fluorescently tagged target protein. Flow cytometric sorting and analyses of libraries, subpopulations or individual clones were followed by SDS-PAGE, western blotting, mass spectrometry and DNA sequencing analyses. For ExLib1, intracellular accumulation of soluble protein was shown to be affected by codon specific effects at some positions of the common N-terminal extension. Interestingly, for ExLib2 where the same sequence window was randomized via seven consecutive NN(G/T) tri-nucleotide repeats, high product levels (up to 24-fold higher than a reference clone) were associated with a preferential appearance of novel SD-like sequences. Possible mechanisms behind the observed effects are discussed.
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Affiliation(s)
| | - Per-Åke Nygren
- *To whom correspondence should be addressed. +46 8 55378328+46 8 55378481
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Lutz S, Fast W, Benkovic SJ. A universal, vector-based system for nucleic acid reading-frame selection. Protein Eng Des Sel 2002; 15:1025-30. [PMID: 12601143 DOI: 10.1093/protein/15.12.1025] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The identification of a nucleic acid sequence's correct reading frame has important implications for homology-independent protein engineering techniques such as incremental truncation and SCRATCHY. We report the development and experimental implementation of a general in-frame selection system, pSALect, a plasmid vector that utilizes two marker sequences flanking the DNA of interest. This dual selection approach overcomes inconsistencies observed with traditional C-terminally fused reporter proteins. In the pSALect vector, sequences of interest are positioned between an N-terminal Tat-signal sequence and a C-terminal beta-lactamase reporter. In-frame selection of the resulting three-domain protein is performed by growing colonies on ampicillin-containing plates, requiring full-length translation in order to link covalently the signal sequence to the lactamase for export into the periplasm. This dual selection scheme has been validated successfully using defined sequences of glycinamide ribonucleotide formyltransferases (GARTs) from Escherichia coli and human and, in contrast to C-terminal fusion systems, proved effective when applied towards the selection of in-frame constructs in an incremental truncation library.
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Affiliation(s)
- Stefan Lutz
- Department of Chemistry, The Pennsylvania State University, 414 Wartik Laboratory, University Park, PA 16802, USA
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