The Protein Man's Blog | A Discussion of Protein Research

Earlier designated as the "garbage bags" used by the biological systems to remove unnecessary biomolecules of the cells, Exosomes, have recently gained popularity as secreted vesicles pivotal for intracellular and intercellular information transfer. Studies have shown the presence of essential RNA and protein cargos in these small vesicles (30-150 nm). The interest in exosome studies have exponentially grown as they can be manoeuvred as minimally diagnostic tools in order to understand biological functions. Proteomics of exosomes are considered the biological fingerprints as they replicate the properties of the parental cell from where they are originated. As a mobile container of vital biomolecules (specialized proteins and RNAs) exosomes are crucial for antigen- presentation, cell-cell communication, waste management, translocation of biomolecules and coagulation.

Over expression of recombinant protein in bacteria can lead to the accumulation of insoluble protein, which aggregates and is sequestered to inclusion bodies. Slow growth rate and low temperatures during protein expression will help in solubility of many over expressed proteins, however some proteins still form Inclusion Bodies. Inclusion Bodies are pure proteins aggregated in bacterial cytoplasm, but sometimes can be formed in periplasm. Though the process of purification is tedious, we can get pure active protein by using various purification steps. Utmost care to be taken during Inclusion Bodies purification as the process is harsh on delicate proteins and may result in the loss of protein activity.

The cloning and expression of proteins to product recombinant proteins is a hugely popular technique that allows for the production of copious quantities of protein that almost mimic native proteins. Although a popular and useful technique, one of the main reasons for its use can also be a drawback.  In some cases, over-expression of the recombinant protein leads to an accumulation of misfolding protein that aggregates and is sequestered into inclusion bodies.   The purification of inclusion bodies is time consuming, involves harsh denaturants, detergents and other chemicals, resulting in damaged and denatured proteins.  If a researcher is successful in extracting these proteins then they must invest more time and effort to refold the denatured proteins. For this reason, researcher's want to prevent their recombinant proteins from ending up in inclusion bodies.

Membrane proteins play a key role in cellular processes including transport of molecules, signal transduction, utilization of energy and maintenance of cell and tissue structures. It has been determined by genome sequencing that around 30% of genes encode membrane proteins. Furthermore, they are pharmacologically significant as 50% of the current drugs target the membrane proteins.  It is therefore of utmost importance to isolate membrane receptor complexes in functional active form for functional and structural studies, crystallization etc. However in spite of their significance, knowledge of structure and function of membrane proteins is lagging behind soluble proteins due to hurdles like low abundance and their isolation in native form from biological membrane. The obstacle of low abundance of membrane protein can be overcome with heterologous expression of these proteins and employing techniques similar to expression of soluble or cytosol proteins. Isolation of membrane proteins from biological membrane is carried out by solubilization and this process needs fine-tuning in order to purify functionally active membrane receptors complexes.