Expression and purification of recombinant FGFR2b protein and investigation of its structural changes due to interaction with toxic metals

Number of pages: 121 File Format: word File Code: 32092
Year: 2014 University Degree: Master's degree Category: Biology - Environment
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  • Summary of Expression and purification of recombinant FGFR2b protein and investigation of its structural changes due to interaction with toxic metals

    Master thesis

    Medical Biotechnology

    Abstract

    Background: Fibroblast growth factors (FGF) and their receptors (FGFR) play an essential role in the cell. Dysregulation of FGF/FGFR signaling pathways is associated with many abnormalities and cancer development. From this group, type 2 fibroblast growth factor receptor plays an essential role in cell signaling and regulation of important biological processes, including cell differentiation and proliferation. Disturbance in the transmission of the message of this receptor is related to several human pathological disorders. In the meantime, poisoning with toxic metals is one of the major problems in cell biology, whose effects on various signaling pathways have been proven.

    Aim: This study was conducted in order to purify the kinase region of FGFR2b and investigate the effect of toxic metals lead, cadmium, nickel, and aluminum on the structure of the kinase region of the fibroblast growth factor receptor type 2.

    Materials and methods: In this experimental study, the recombinant protein was expressed and purified using pLEICS-01 plasmid, BL21 bacteria, IPTG induction, electrophoresis and Ni2+-NTA column. The activity of the protein sample after dialysis was checked by interaction with SH2 region of phospholipase (PLC) C normal and mutant by PAGE method. The fluorescence spectrum, CD, FTIR and chemical denaturation of the purified protein were investigated and evaluated in the presence of different concentrations of lead, cadmium, nickel and aluminum.

    Findings: SDS-PAGE analysis before and after induction showed that the expressed protein is soluble at 20°C. PAGE results confirmed the activity of the purified protein. Fluorescence spectroscopy showed a decrease in emission intensity with a gradual increase in the concentration of all four toxic metals. The CD spectrum showed that the kinase region under our study has more beta composition than alpha, and the presence of cadmium, nickel and aluminum in the solution does not change the second structure of the kinase, but lead is able to change this structure. The test performed by FTIR also confirmed the effect of lead. Chemical denaturation of the tertiary structure in the presence of cadmium, nickel and aluminum did not change the kinase domain. But this change was observed in the presence of lead.

    Discussion and conclusion: According to the findings, the kinase region of the recombinant fibroblast growth factor 2b receptor, which is a 38 kilodalton protein, was produced and purified, and it was shown to be soluble and active. Changes in the third and second structure of the kinase region caused its instability in the presence of lead. This instability at the molecular level can disrupt the cell's signaling pathway. However, this instability was not observed in the presence of cadmium, nickel, and aluminum.

    Keywords: fibroblast growth factor receptor, kinase region, signaling, toxic metals, fluorescence spectroscopy, CD, FTIR

    Chapter One

    Introduction and importance of the topic

    Introduction

    1-1-1- Fibroblast growth factor

    Fibroblast growth factor or FGF (Figure 1) is a protein that plays a role in many cellular processes such as cell division, embryo development, angiogenesis and many other processes. In addition, this protein is added as an important factor to the culture medium of human embryonic stem cells so that the cells can be preserved and propagated in a fundamental state without differentiation (1). They play a role in cell survival, migration and differentiation (2). Cell metabolism, tissue repair, angiogenesis, and the development of embryonic stages are among the tasks that are performed in the body during fetal and adult life by these receptors by binding to fibroblast growth factors (FGF) (3). Mutated forms of fibroblast growth factor receptors are known in several cancers, including lung, breast, stomach, brain, head and neck, prostate, colon, uterus, bladder, and multiple myeloma (4-6).Imbalance in FGFR signaling is associated with several human pathological disorders such as skeletal syndromes (4). In the meantime, FGFR2 plays an important role in tissue growth and repair, especially bone and blood vessels. Figure 1: How FGF and FGFR function in general. Fibroblast growth factor receptors (FGFR). This protein has 334 amino acids and an approximate molecular weight of 38 kilodaltons. Genetic changes in this receptor are related to endometrial, ovarian and breast cancers.  It is worth mentioning that the mutant type of this receptor has been reported in a number of cancers, which is related to the increase of messages related to this receptor (7).

    In this recombinant protein, by transferring the mutation pattern observed in the receptor expressed in cancer cells, an active and recombinant form of the tyrosine kinase region of the FGFR2b protein has been created, which has the desired mutations. It is worth mentioning that the preparation of the tyrosine kinase region of the FGFR2b protein in a pure form makes it possible to obtain information about the structure and the interaction between the protein and the ligand, including the effect of various inhibitors on the kinase region of this protein.

    Accordingly, in this research, the structural changes of the recombinant FGFR2b protein due to the interaction with the mentioned metals are investigated.

    Figure 2: Type 2 fibroblast growth factor receptor.

    1-1-4- Fibroblast growth factor tyrosine kinase receptors

    Fibroblast growth factor receptors belong to a family of tyrosine kinase receptors (Figure 3). These receptors have two isoforms, b and c, which are expressed in epithelial and mesenchymal tissues, respectively. Also, seven receptors are included in the family of fibroblast growth factor receptors (Figure 3), which include FGFR1b, FGFR1c, FGFR2b, FGFR2c, FGFR3b, FGFR3c and FGFR4(8). These receptors play a key role in the cell signaling pathway in regulating biological processes including cell proliferation, survival, migration and cell differentiation (9). All of them have an intramembrane part, an extracellular region that binds to the ligand, and an intracellular region that has tyrosine kinase properties. The FGFR2b receptor is the epithelial isoform of the fibroblast growth factor receptor. The FGFR2b kinase region consists of 334 amino acids and has a structure of two N-terminal and C-terminal kinase regions that are connected by a flexible linker region. This connecting region is also called the activation loop, which plays an important role in the tyrosine phosphorylation of the receptor kinase region. Approximately 20% of human genes encode products that participate in cellular signaling pathways. The main regulators of these pathways act through phosphorylation/dephosphorylation reactions. Tyrosine kinase enzymes are a group of enzymes that are responsible for tyrosine amino acid phosphorylation on their target protein. There are two families of tyrosine kinase enzymes, which are membrane-bound kinase receptors and cytoplasmic kinases, which are not receptors. The catalytic region of tyrosine kinase includes a specific ATP molecule binding site and a substrate binding site (10). Non-regulated signaling pathways in FGF / FGFR is associated with many disorders and cancer. From the department of fibroblast growth factor receptor type II in cellular signal transduction and regulation of important biological processes including cell proliferation and differentiation is essential. Impaired signaling of these receptors is associated with several human pathologies. The toxic metal poisoning is one of the major problems in cell biology, effects on different signaling pathways have been demonstrated.

  • Contents & References of Expression and purification of recombinant FGFR2b protein and investigation of its structural changes due to interaction with toxic metals

    List:

    Chapter One Introduction and importance of the topic. 3

    1-1- Introduction. 4

    1-1-1- fibroblast growth factor. 4

    1-1-2- fibroblast growth factor receptors. 4

    1-1-3- type 2 fibroblast growth factor receptors. 5

    1-1-4- fibroblast growth factor tyrosine kinase receptors. 6

    1-1-5- activation of kinases through mutation. 8

    1-2- The importance of the topic and the necessity of conducting research. 9

    1-3- Plan objectives. 9

    1-3-1- the main goal. 9

    1-3-2- Secondary objectives. 9

    1-3-3- practical goals. 10

    1-3-4- Assumptions. 10

    1-3-5- Variables. 10

    The second chapter Review of past texts. 11

    2-1- protein. 12

    2-1-1- The structure of proteins. 13

    2-1-2-tyrosine kinase receptors. 17

    2-1-3- fibroblastic growth factors. 18

    2-1-4- fibroblast growth factor receptors. 20

    2-1-5- fibroblast growth factor receptors and pathological disorders. 22

    2-1-6- cellular signaling pathway of fibroblast growth factors. 25

    2-1-7- Regulation of fibroblast growth factor signaling pathway. 29

    2-2- What is metal?. 31

    2-2-1- Toxic metals. 31

    2-2-3- Lead. 32

    2-2-4-Cadmium. 32

    2-2-5- Nickel. 33

    2-2-6-aluminum. 33

    2-7- The effect of metals on signaling pathways. 34

    2-7-1-ROS. 34

    2-7-2-MAPK. 35

    2-7-3-PI3K/Akt 36

    2-7-4-HIF. 37

    2-7-5- NF-?B. 38

    2-7-6-NFAT. 39

    2-7-7- AP. 40

    2-8- Effect of metal compounds on signaling pathways and gene expression. 41

    2-8-1- lead. 41

    2-8-2- Cadmium. 43

    2-8-3- Nickel. 46

    2-8-4- Aluminum. 48

    2-9- Predicting the structure of proteins. 50

    2-9-1- Examining the structure of proteins. 50

    2-9-2- Structural study of proteins. 51

    2-9-3- Techniques for studying the structure of proteins. 52

    2-9-4- spectroscopic fluorescence technique. 53

    2-9-5- Circular dilation technique (CD) 56

    2-9-6- Denaturation techniques and agents. 57

    2-10- Production and purification techniques of recombinant proteins. 60

    2-10-1- Use of recombinant proteins. 60

    2-10-2- Recombinant proteins 60

    2-10-3- Production of recombinant proteins in plants. 63

    2-10-4- Using Escherichia coli as a host organism for protein production 64

    2-10-5- Purification of recombinant proteins. 64

    Chapter 3 materials and methods. 66

    3-1- Test materials, equipment and variables. 67

    3-1-1- Materials used in the experiment. 67

    3-1-2- Devices and equipment used in testing. 68

    3-2- Solutions and buffers. 69

    3-2-1- Preparation of ampicillin stock. 69

    3-2-2- Preparation of IPTG stock. 70

    3-2-3- Preparation of cell lysing buffer to check protein solubility. 70

    3-2-4- preparation of cell lysing buffer for protein purification. 70

    3-2-5- Preparation of 4% polyacrylamide gel solution. 70

    3-2-6- Preparation of 12% polyacrylamide gel solution. 71

    3-2-7- Preparation of 10% APS solution. 71

    3-2-8- Preparation of x10 electrode buffer (Running buffer) 71

    3-2-9- Preparation of Sample Buffer) 71

    3-2-10- Preparation of 0.5 M Tris-Hcl solution. 72

    3-2-11- Preparation of 1.5 M Tris-Hcl solution. 72

    3-2-12- Preparation of Staining Buffer. 72

    3-2-13- Preparation of Destaining Buffer. 73

    3-2-14- Preparation of acrylamide-bisacrylamide solution. 73

    3-2-15- Preparation of SDS buffer. 73

    3-2-16- Preparation of buffer A (Washing Buffer) 73

    3-2-17- Preparation of buffer B (Eluting Buffer. 74

    3-2-18- Preparation of dialysis buffer. 74

    3-2-19- Preparation of guanidine hydrochloride stock (GnHCl) 74

    3-2- Preparation of metal stocks 74 3-3 Preparation of recombinant plasmid pLEICS-01 and recombinant protein tyrosine sequence 75

    3-2- Recombinant protein production steps

    3-3- Determination of protein concentration

    3-3-Spectroscopic studies83

    3-3-4- Fluorescence spectroscopic studies. 83

    3-3-5- CD ring imaging spectroscopic studies) 85

    3-3-6- FTIR spectroscopic studies. 86

    3-3-7-Chemical denaturation studies using fluorescence spectroscopy 87

            Chapter 4 findings and results. . 88

    4-1- Examining protein expression at 37°C. 88

    4-2- Examination of protein expression at 20 degrees Celsius. 89

    4-3- Investigating the solubility of expressed protein at two temperatures of 20 and 37 degrees Celsius. 90

    4-4- Checking the purity of dissolved protein. 91

    4-5- SDS-PAGE analysis after dialysis. 92

    4-6- Investigating the function of purified protein. 93

    4-7- Investigating the tertiary structure of the tyrosine kinase region of the recombinant FGFR2b protein 94

    4-8- Investigating the effect of chemical denaturation on the maximum wavelength of the intrinsic fluorescence emission of the tyrosine kinase region of the recombinant FGFR2b protein 98

    4-9- Investigating the effect of chemical denaturation on the intensity of the intrinsic fluorescence emission of the protein tyrosine kinase region Recombinant FGFR2b 101

    4-10- Investigating the effect of lead, cadmium, aluminum and nickel on the second structure of the tyrosine kinase region of recombinant FGFR2b protein 104

    Chapter 5 Discussion and conclusion. 109

    5-1- Discussion and conclusion. 110

    List of references: 116

    .Abstract

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Expression and purification of recombinant FGFR2b protein and investigation of its structural changes due to interaction with toxic metals