Eukaryotic cells are characterized by extensive subcellular compartmentation whose structural basis is the existence of a number of highly specialized membrane-bound organelles. Each of these organelles is equipped with a specific subset of proteins allowing them to fulfill specific tasks in cellular metabolism. Mitochondria are present in virtually all eukaryotic cells. Mitochondria are the compartments responsible for respiration and oxidative phosphorlyation. They are made up of two highly specialized membrane systems, the OM (Outer Membrane) and IM (Inner Membrane), and two aqueous compartments, the Matrix and the IMS (Intermembrane Space). More than 90% of the mitochondrial proteins are encoded on the nuclear DNA and then synthesized as precursors on cytosolic[..]

Coagulation is a dynamic process which involves the regulated sequence of proteolytic activation of a series of zymogens to achieve appropriate and timely haemostasis in an injured vessel, in an environment that overwhelmingly favours an anticoagulant state [Ref.1 & 2]. There are two main mechanisms for triggering the blood clotting, termed as the contact pathway/intrinsic pathway and the tissue factor pathway/extrinsic pathway [Ref.3].The contact pathway of coagulation is initiated by activation of factor XII (fXII) in a process that also involves high-molecular-weight kininogen (HK) and plasma prekallikrein (PK). Contact of blood with an artificial surface leads to a change in the conformation of fXII, resulting in the generation of small amounts of active factor XII[..]

Splicing of pre-mRNA (pre-mRNA) is a complex mechanism where introns are removed, and exons are joined together to form a mature mRNA competent for translation. Pre-mRNA splicing is tightly regulated and its failure is linked to various tumors, pathologies of the endocrine system and neurodegenerative disorders. The discovery that introns are removed during splicing came from electron microscopy of RNA-DNA hybrids between adenovirus DNA and the mRNA encoding Hexon, a major virion capsid protein. For short transcription units, RNA splicing usually follows cleavage and polyadenylation of the 3’ end of the primary transcript. But for long transcription units containing multiple exons, splicing of exons in the nascent RNA usually begins before transcription of the[..]

The nuclei of all eukaryotic cells contain three different RNA Polymerases, designated I, II and III. Like the DNA Polymerase that catalyzes DNA replication, RNA Polymerases catalyze the formation of the phosphodiester bonds that link the nucleotides together to form a linear chain. Each eukaryotic RNA Polymerase catalyzes transcription of genes encoding different classes of RNA. Transcription by RNA Polymerase-III produces small, stable RNAs including tRNAs, the 5S rRNA associated with the large ribosomal subunit, one of the snRNA (small nuclear RNAs) required for pre-mRNA splicing, and the 7S RNA associated with the signal recognition particle involved in secretion of proteins and the insertion of membrane-spanning proteins into cellular membranes. The func¬tions[..]

The nuclei of all eukaryotic cells contain three different RNA Polymerases, designated I, II and III. Like the DNA Polymerase that catalyzes DNA replication, RNA Polymerases catalyze the formation of the phosphodiester bonds that link the nucleotides together to form a linear chain. Each eukaryotic RNA Polymerase catalyzes transcription of genes encoding different classes of RNA. RNA Polymerase-II catalyzes transcription of all protein-coding genes; that is, it functions in production of mRNAs. RNA Polymerase-II also produces four snRNAs (small nuclear RNAs) that take part in RNA splicing.The eukaryotic polymerases do not directly recognize their core promoter sequences. The first step in complex formation at a promoter containing a TATA Box is binding of the factor[..]

A cell must selectively translocate molecules across its plasma membrane to maintain the chemical composition of its cytoplasm distinct from that of the surrounding milieu. The most intriguing and, arguably, the most important membrane proteins for this purpose are the ABC (ATP-Binding Cassette) transporters. These proteins, found in all species, use the energy of ATP hydrolysis to translocate specific substrates across cellular membranes. The chemical nature of the substrates handled by ABC transporters is extremely diverse--from inorganic ions to sugars and large polypeptides--yet ABC transporters are highly conserved (Ref.1).Transporters have been classified as primary, secondary, or tertiary active transporters. Secondary or tertiary active transporters, such as[..]

HBV (Hepatitis-B Virus) belongs to a family of closely related DNA viruses called the Hepadnaviruses. Included in this family are the WHV (Woodchuck Hepatitis Virus), the DHBV (Duck Hepatitis-B Virus) and several other avian and mammalian variants. Hepadnaviruses have a strong preference for infecting liver cells, but small amounts of hepadnaviral DNA can be found in kidney, pancreas, and mononuclear cells. However, infection at these sites is not linked to extra hepatic disease (Ref.1). The HBV nucleocapsid contains a relatively small and partially duplex 3.2 Kb circular DNA, viral polymerase and core protein. The genome has only four long open reading frames. The preS–S (presurface–surface) region of the genome encodes the three viral surface antigens by[..]

HBV(Hepatitis B virus) is a member of the family Hepadnaviridae. It is a hepatotropic non-cytopathic DNA virus and is a major cause of acute and chronic hepatitis in humans. As HBV itself is currently viewed as a non-cytopathic virus, the liver pathology associated with hepatitis B is mainly thought to be due to immune responses directed against HBV antigens. The outcome of HBV infection is the result of complex interactions between replicating HBV and the immune system.Both innate and adaptive arms of the immune system are generally involved in responding to the viral infection, with innate responses being important for control of viral replication and dissemination very early after infection, as well as for timely orchestration of virus-specific adaptive responses.[..]

Poxviridae is a family of viruses containing large double-stranded DNA genomes of 130,000 to >300,000 nucleotides.  Humans, vertebrates, and arthropods serve as natural hosts. Poxviridae viral particles (virions) are generally enveloped (external enveloped virion), though the intracellular mature virion form of the virus, which contains different envelope, is also infectious. They vary in their shape depending upon the species but are generally shaped like a brick or as an oval form similar to a rounded brick because they are wrapped by the endoplasmic reticulum. The virion is exceptionally large its size is around 200 nm in diameter and 300 nm in length and carries its genome in a single, linear, double-stranded segment of DNA. By comparison, Rhinovirus is[..]

Poliovirus is a member of the Picornaviridae family, which includes a number of significant pathogens of humans (e.g., Rhinoviruses, Coxsackieviruses, Echoviruses, Enteroviruses, and Hepatitis-A virus) and livestock (e.g., foot-and-mouth disease viruses). Poliovirus has three known serotypes: PV1, PV2, and PV3 and all three serotypes can cause poliomyelitis, a paralytic disease resulting from the destruction of motor neurons in the CNS (Central Nervous System )(Ref.1). All the three serotypes of Poliovirus recognize a common cellular receptor, CD155 (or PVR, Poliovirus Receptor), for cell attachment and entry. CD155 is a trans-membrane glycoprotein belonging to the immunoglobulin super family. CD155 also functions as a cell adhesion protein and aids in transendothelial[..]

Diabetes mellitus is a chronic disease characterized by high blood glucose levels that requires long-term medical attention both to limit the development of its devastating complications and to manage them when they do occur. The pancreatic Beta-cell and its secretory product insulin are central in the pathophysiology of diabetes. There are two main types of diabetes, Type-I, which is insulin dependent, and Type-II, which is non-insulin dependent. Type-II diabetes is a complex and heterogeneous disease caused by both environmental and genetic factors. It maybe of various forms each of which is characterized by variable degrees of insulin resistance and Beta-cell dysfunction, and which together lead to hyperglycemia. At each end of this spectrum are single gene[..]

Influenza (mostly referred to as “flu”) is a contagious viral infection caused primarily by the influenza virus A or B. It affects mainly the upper respiratory organs (i.e., the nose, throat, bronchi, and infrequently, lungs) but other organs such as the heart, brain, and muscles can be involved. It occurs worldwide and causes considerable morbidity and mortality with pandemic, epidemic, or seasonal patterns. Typical Influenza illness includes fever and respiratory symptoms, such as cough, sore throat, runny or stuffy nose, as well as headache, muscle aches, and often extreme fatigue. Although nausea, vomiting, and diarrhea can sometimes accompany Influenza infection, especially in children, these symptoms are rarely the primary symptoms. Most people[..]