Research Journal of Pharmaceutical, Biological and Chemical

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ABSTRACT

There is no substance as important as deoxyribonucleic acid as it carries within its own structure the hereditary in formations that determines the structure of proteins, the important molecule of life. Deoxyribonucleic acid transcribe messenger ribonucleic acid which finally translates protein the essential macromolecules. Through gene expression the information contained in gene can be utilized for the synthesis of functional gene product which is often a protein or an enzyme required for the cellular function of live organisms. This article discusses about the various strategies required for the expression of gene to get gene product. It also highlighted few expression systems required to express gene. The author also explained the strategies regarding the purification of expressed proteins. In this context protein affinity tags were explored and highlighted. This review suumarized the role of His-tag, GST-tag, MBP-tag, IMPACT, TAP-Tagging towards protein purification. The aim of writing this review article is to attract those researchers working in the field of gene expression and protein purification to find new molecules for better therapy.

Keywords: Proteins, Vectors, Expression system, Recombinant protein purification, Affinity protein purification tags.

INTRODUCTION

One of the most important scientific legacies that our generations will handover to the successors is the detailed and elaborated information about biological sequences and structure now being determined and achieved. Deoxyribonucleic acid (DNA), the genetic material, is a long unbranched polymer having the four deoxynucleoside monophosphate namely deoxyadenosine monophosphate (dAMP), deoxythymidine monophosphate (dTMP), deoxyguanosine monophosphate (dGMP) and deoxycytidine monophosphate (dCMP). Nucleic acid is a biological molecule essential for life as it encodes for protein. Proteins are the major functional molecules of life whose properties are so useful that we employ them as therapeutic agents, catalysts and materials. Many diseases stem from mutation in proteins that cause them to loose function. In some cases, catalytic activity may be impaired, and so metabolic pathways may be altered. The example is phenylketonaria. In other cases , structural properties may be impaired, leading to a loss of physical function as seen in the case of muscular dystrophy. The ultimate goal of protein science is to be able to predict the structure and activity of a protein de novo and how it will bind to ligand. When this is achieved, we will be able to design and synthesize novel catalyst, materials, and drugs that will eliminate disease and minimize ill health. Genetic engineering has revolutionized protein science. First recombinant DNA technology has enabled the production of large quantities of proteins that were previously either unknown or valuable only in small quantities. Second it has allowed rapid sequencing of proteins from their DNA. Third it has allowed the facile modification of protein structure by mutation of their genes. This has lead to protein engineering. Protein engineering is of fundamental importance in analyzing structure function relationships in proteins and producing novel proteins for biomedical and biotechnological use. A gene is defined as a discrete unit of genetic information that can be utilized for the synthesis of polypeptide. It includes the coding sequence, the promoter, terminator and introns. In protein production there are two aspects which require optimization that is the biology of the system and the production process itself. In order to express a gene in an efficient manner, the gene has to be inserted into an appropriate vector containing a suitable promoter. This can then be transferred into a suitable host using the modern technology. Now a days a variety of vectors as well as expression systems are available to express gene of interest. This article is totally based on literature survey. This article has been compiled by the author by using modern and traditional methods of literature survey. The search engines used in the survey were Science direct, PubMed, Google etc. In addition to this the author also took the help of books and journals for making this manuscript. The literatures cited in this article are not limited to a particular region but is considered more or less from the entire globe. Recent research has been focused by this author. Literatures for the past ten years were paid more attention. Moreover the valuable literatures were also efficiently highlighted in this manuscript. In his previous articles the author highlighted a number of vectors that can be used in gene manipulation. In addition to this the author in his another article has described a number of gene transfer technologies that can manipulate gene in plants. Prior to this work the author of this article has reported about the technologies related to transgenic animals. He also described DNA vaccine. In this article the author summarized the systems used in expressing gene. He also explored and presented the technologies that can be used to purify proteins..The author described the expression of genes in various systems like bacteria, yeast, insect and mammals. Much effort was given to the proteins affinity tag that makes the purification step easy and improves the purity and stability of recombinant protein. The aim of writing this article is to help the new researchers who are approaching the technology of gene expression and protein purification to prepare the products having high therapeutic values for living beings. A number of systems have been described below that can be used for the expression of gene. The main objective of this review article is to make awareness in the young researchers about the systems used to express gene and to purify the expressed protein.