Inteins Research Papers - Academia.edu (original) (raw)

Split inteins link their fused peptide or protein sequences with a peptide bond in an autocatalytic reaction called protein trans-splicing. This reaction is becoming increasingly important for a variety of applications in protein... more

Split inteins link their fused peptide or protein sequences with a peptide bond in an autocatalytic reaction called protein trans-splicing. This reaction is becoming increasingly important for a variety of applications in protein semisynthesis, polypeptide circularisation, construction of biosensors, or segmental isotopic labelling of proteins. However, split inteins exhibit greatly varying solubility, efficiency and tolerance towards the nature of the fused sequences as well as reaction conditions. We envisioned that phage display as an in vitro selection technique would provide a powerful tool for the directed evolution of split inteins with improved properties. As a first step towards this goal, we show that presentation of active split inteins on an M13 bacteriophage is feasible. Two different C-terminal intein fragments of the Ssp DnaB intein, artificially split at amino acid positions 104 and 11, were encoded in a phagemid vector in fusion to a truncated gpIII protein. For efficient production of hybrid phages, the presence of a soluble domain tag at their N-termini was necessary. Immunoblot analysis revealed that the hybrid phages supported protein trans-splicing with a protein or a synthetic peptide, respectively, containing the complementary intein fragment. Incorporation of biotin or desthiobiotin by this reaction provides a straightforward strategy for future enrichment of desired mutants from randomised libraries of the C-terminal intein fragments on streptavidin beads. Protein semisynthesis on a phage could also be exploited for the selection of chemically modified proteins with unique properties.

Uric acid, a side product of nucleotide metabolism, should be cleared from blood stream since its accumulation can cause cardiovascular diseases and gout. Uricase (urate oxidase) converts uric acid to 5-hydroxyisourate, but it is absent... more

Uric acid, a side product of nucleotide metabolism, should be cleared from blood stream since its accumulation can cause cardiovascular diseases and gout. Uricase (urate oxidase) converts uric acid to 5-hydroxyisourate, but it is absent in human and other higher apes. Yet, the recombinant form of uricase, Rasburicase, is now commercially available to cure tumor lysis syndrome by lowering serum uric acid level. Developing new methods to efficiently purify pharmaceutical proteins like uricase has attracted researchers' attention. Self-cleaving intein mediated single column purification is one of these novel approaches. Self-cleaving inteins are modified forms of natural inteins that can excise and join only at one junction site. In this study, the synthetic gene of Aspergillus flavus uricase, a homotetrameric protein, was cloned into pTXB1 vector as a fusion with the N-terminal of Mxe GyrA intein and chitin-binding domain (CBD) for simple purification. Expression was confirmed by ...

The increase of publicly available sequencing data has allowed for rapid progress in our understanding of genome composition. As new information becomes available we should constantly be updating and reanalyzing existing and newly... more

The increase of publicly available sequencing data has allowed for rapid progress in our understanding of genome composition. As new information becomes available we should constantly be updating and reanalyzing existing and newly acquired data. In this report we focus on transposable elements (TEs) which make up a significant portion of nearly all sequenced genomes. Our ability to accurately identify and classify these sequences is critical to understanding their impact on host genomes. At the same time, as we demonstrate in this report, problems with existing classification schemes have led to significant misunderstandings of the evolution of both TE sequences and their host genomes. In a pioneering publication Finnegan (1989) proposed classifying all TE sequences into two classes based on transposition mechanisms and structural features: the retrotransposons (class I) and the DNA transposons (class II). We have retraced how ideas regarding TE classification and annotation in both...

In this study, several expression strategies were investigated in order to develop a generic, highly productive and efficient protocol to produce nanobodies modified with a clickable alkyne function at their C-terminus via the... more

In this study, several expression strategies were investigated in order to develop a generic, highly productive and efficient protocol to produce nanobodies modified with a clickable alkyne function at their C-terminus via the intein-mediated protein ligation (IPL) technique. Hereto, the nanobody targeting the vascular cell adhesion molecule 1 (NbVCAM1) was used as a workhorse. The highlights of the protocol can be ascribed to a cytoplasmic expression of the nanobody-intein-chitin-binding domain fusion protein in the Escherichia coli SHuffle(®) T7 cells with a C-terminal extension, i.e. LEY, EFLEY or His6 spacer peptide, in the commonly used Luria-Bertani medium. The combination of these factors led to a high yield (up to 22 mg/l of culture) and nearly complete alkynation efficiency of the C-terminally modified nanobody via IPL. This yield can even be improved to ∼45 mg/l in the EnPresso(®) growth system but this method is more expensive and time-consuming. The resulting alkynated n...

The identification of environmental factors that lead to loss of tolerance has been coined the Holy Grail of autoimmunity. Our work has focused on the reactivity of antimitochondrial autoantibodies (AMA) to chemical xenobiotics and has... more

The identification of environmental factors that lead to loss of tolerance has been coined the Holy Grail of autoimmunity. Our work has focused on the reactivity of antimitochondrial autoantibodies (AMA) to chemical xenobiotics and has hypothesized that a modified peptide within PDC-E2, the major mitochondrial autoantigen, will have been immunologically recognized at the time of loss of tolerance. Herein we successfully applied intein technology to construct a PDC-E2 protein fragment containing amino acid residues 177-314 of PDC-E2 by joining a recombinant peptide spanning residues 177 to 252 (PDC-228) with a 62 residue synthetic peptide from 253 to 314 (PP), which encompasses PDC-E2 ILD. We named this intein-constructed fragment PPL. Importantly, PPL, as well as lipoic acid conjugated PPL (LA-PPL) and xenobiotic 2-octynoic acid conjugated PPL (2OA-PPL), are recognized by AMA. Of great importance, AMA has specificity for the 2OA modified PDC-E2 ILD peptide backbone distinct from ant...

Introduction Ataxia telangiectasia (AT) is an autosomal recessive multisystem disorder characterized by variable immunodeficiency, progressive neurodegeneration, occulocutaneous telangiectasia, and an increased susceptibility to... more

Introduction Ataxia telangiectasia (AT) is an autosomal recessive multisystem disorder characterized by variable immunodeficiency, progressive neurodegeneration, occulocutaneous telangiectasia, and an increased susceptibility to malignancies. This study was designed to study the role of proapoptotic BAK, BAX, and NBK/BIK genes in a group of patients with AT to elucidate the possible role of these genes in progression of malignancies in this disease. Materials and Methods Fifty Iranian patients with AT were investigated in this study. The entire coding regions of the BAK gene (exons 2–6), NBK/BIK gene (exons 2–5), and BAX gene (exons 1–7) were amplified using polymerase chain reaction (PCR). The PCR products were separated by 2% agarose gel electrophoresis, and all positive samples were verified by direct sequencing of PCR products using the same primers used for PCR amplification, BigDye chemistry, and Avent 3100 Genetic Analyzer following the manufacturer’s instructions (Applied Biosystems). Results Eight of fifty Iranian AT patients (16%) exhibited a C > T transition in exon 2 (c342C > T) of the BAK gene, while none of the healthy controls had such alteration (P = 0.0001). Higher frequency of another nucleotide substitution in the noncoding region of exon 7 in BAX gene (6855G > A) was also identified in 68% of the patient group versus 24% in the controls (P < 0.0001). Sequence alteration in intronic region of the NBK/BIK gene IVS4-12delTC was observed in 52% of AT patients, which was significantly higher than 20% in the control group (P = 0.0023). Another variant IVS1146C > T in the intronic region of the BAX gene was found in 78% of patients, which was significantly higher than 10% in the controls (P < 0.0001). Frequency of alteration in intronic region of exon 3 of the BAX gene (IVS3 + 14A > G) was also significantly higher in the AT patients (P < 0.0001). Discussion Several alterations in the proapoptotic genes BAK, NBK/BIK, and BAX were found in our study, which could elucidate involvement of the mitochondrial pathway mediated apoptosis in accelerating and developing of cancers and in immunopathogenesis of AT. Such altered apoptosis in AT could play some roles in developing cancers in this group of patients.

Self splicing introns and inteins that rely on a homing endonuclease for propagation are parasitic genetic elements. Their life-cycle and evolutionary fate has been described through the homing cycle. According to this model the homing... more

Self splicing introns and inteins that rely on a homing endonuclease for propagation are parasitic genetic elements. Their life-cycle and evolutionary fate has been described through the homing cycle. According to this model the homing endonuclease is selected for function only during the spreading phase of the parasite. This phase ends when the parasitic element is fixed in the population. Upon fixation the homing endonuclease is no longer under selection, and its activity is lost through random processes. Recent analyses of these parasitic elements with functional homing endonucleases suggest that this model in its most simple form is not always applicable. Apparently, functioning homing endonuclease can persist over long evolutionary times in populations and species that are thought to be asexual or nearly asexual. Here we review these recent findings and discuss their implications. Reasons for the long-term persistence of a functional homing endonuclease include: More recombinat...

Chemical-enzymatic synthesis of human Epidermal Growth Factor (hEGF) cDNA has been performed, following by cloning into expression vector pTWIN1 (New England Biolabs). The resulting recombinant fusion protein expressed in Escherichia coli... more

Chemical-enzymatic synthesis of human Epidermal Growth Factor (hEGF) cDNA has been performed, following by cloning into expression vector pTWIN1 (New England Biolabs). The resulting recombinant fusion protein expressed in Escherichia coli consisted of the N-terminal chitin-binding domain, mini-intein Ssp dnaB domain and hEGF polypeptide at the C-terminus. In this construct, mini-intein Ssp dnaB played a role of catalytically active subunit capable under certain conditions of autocatalytic cleavage resulting in separation of the target protein. As the hybrid protein had several cysteins in its sequence-one in chitin-binding domain, one in mini-intein and six in hEGF, it was necessary to work out optimal scheme for refolding and purification of the recombinant hEGF. As a result of this work, two schemes of the recombinant hEGF purification have been developed: according to the first scheme, the recombinant protein with reduced cysteins is bound to the chitin column, the hEGF is cleave...

Dopamine- and cAMP-regulated phosphoprotein of relative molecular mass 32kDa (DARPP-32) plays a pivotal role in the signal transduction of several neurotransmitters and neuromodulators that are implicated in the pathophysiology of a... more

Dopamine- and cAMP-regulated phosphoprotein of relative molecular mass 32kDa (DARPP-32) plays a pivotal role in the signal transduction of several neurotransmitters and neuromodulators that are implicated in the pathophysiology of a variety of neuropsychiatric disorders. A postmortem study reported a significantly reduced DARPP-32 expression in the dorsolateral prefrontal cortex (DLPFC) of patients with schizophrenia, suggesting possible involvement of DARPP-32 in the pathophysiology of schizophrenia. Hence, DARPP-32 was considered as a candidate gene for schizophrenia in this study. We first systemically searched for mutations in the DARPP-32 gene in 50 Han Chinese patients with schizophrenia from Taiwan. Five molecular variants were identified, including a C-to-G substitution (g.-2036C&amp;amp;amp;amp;amp;amp;gt;G) in the putative core promoter that obliterated a predictive AP-2 transcription factor binding site, a G deletion in the untranslated exon 2 (g.1238delG), a G-to-A and an A-to-G substitutions in intron 2 (IVS2+31G&amp;amp;amp;amp;amp;amp;gt;A) and intron 6 (IVS6+32A&amp;amp;amp;amp;amp;amp;gt;G), respectively, and a three-base pair deletion of AGA in exon 6 that resulted in deletion of a glutamate at codon 135 (E135del). Further SNP- and haplotype-based association study in 249 patients and 273 control subjects, however, did not detect association of these markers with schizophrenia. Hence, our results suggest that the reduced DARPP-32 protein in patients with schizophrenia is unlikely caused by mutations in the DARPP-32 gene itself and the DARPP-32 gene is also unlikely a major susceptibility gene for schizophrenia. Nevertheless, the identification of these molecular variants should help the study of gene regulation and structure-function relationship of DARPP-32, and the association study of DARPP-32 gene with other neuropsychiatric disorders.

In this review, a targeted cancer therapeutic is proposed providing direct targeting of tumor-specific or -associated antigens from within malignant cells: (i) with an antibody-based biological agent; (ii) utilizing a constitutively active... more

In this review, a targeted cancer therapeutic is proposed providing direct targeting of tumor-specific or -associated antigens from within malignant cells: (i) with an antibody-based biological agent; (ii) utilizing a constitutively active apoptosis effector that is inhibited or nonfunctional until the antibody binds its agonist.Two possible configurations to achieve this end are provided. One embeds an scFv control into the apoptosis-inducing effector using an intein and the second employs a zinc-finger-based targeting and activating mechanism based on an approach known as sequence-enabled reassembly of proteins. Although the latter might provide a broader range of targets, because zinc fingers bind directly to DNA rather than transcribed protein, this review focuses on the former owing to the large body of clinical data available.

Erratum to: J Clin ImmunolDOI 10.1007/s10875-009-9340-6The original version of this article unfortunately contained a mistake. The last name of one of the authors is incorrect. “Asghar Agamohammadi” should be “Asghar Aghamohammadi.”

An intein-driven protein splicing approach allowed for the covalent linkage between the N-and C-termini of a polypeptide chain to create circular variants of the endo-β-1,3-1,4-glucanase, LicA, from Bacillus licheniformis. Two circular... more

An intein-driven protein splicing approach allowed for the covalent linkage between the N-and C-termini of a polypeptide chain to create circular variants of the endo-β-1,3-1,4-glucanase, LicA, from Bacillus licheniformis. Two circular variants, LicA-C1 and LicA-C2, which have connecting loops of 20 and 14 amino acids, respectively, showed catalytic activities that are approximately two and three times higher, respectively, compared to that of the linear LicA (LicA-L1). The thermal stability of the circular variants was significantly increased compared to the linear form. Whereas the linear glucanase lost half of its activity after 3 min at 65 °C, the two circular variants have 6-fold (LicA-C1) and 16-fold (LicA-C2) increased half-life time of inactivation. In agreement with this, fluores-cence spectroscopy and differential scanning calorimetry studies revealed that circular enzymes undergo structural changes at higher temperatures compared to that of the linear form. The effect of calcium on the conformational stability and function of the circular LicAs was also investigated, and we observed that the presence of calcium ions results in increased thermal stability. The impact of the length of the designed loops on thermal stability of the circular proteins is discussed, and it is suggested that cyclization may be an efficient strategy for the increased stability of proteins.