A Conventional and 2DCOS Infrared Approach to the Kinetics of Protein Misfolding

Igor      de la Arada; Nagore      Andraka; Marcos      Garcia Pacios; Jose      Luis R. Arrondo

Abstract

Cell viability depends on the correct folding of the proteins involved in metabolism. Proteins are synthesized on the endoplasmic reticulum and must follow a pathway to a correct, metastable, tridimensional structure. Changes in structure or in environmental conditions can drive an instability of the folding conditions and produce non-active aggregates that in principle are proteolysed by the cellular mechanisms. However, these aggregates can be even more stable than the native proteins, escaping the cellular control. They can be classified as amorphous, if there is not a well-organized structural pattern, or ordered if a repetitive pattern is produced. These ordered structures, known as fibrils, are involved in many diseases. Infrared spectroscopy is a method of choice to study its formation because it is not affected by turbidity or the formation of high molecular weight aggregates. Moreover, in both cases, two bands characteristic of intermolecular - sheets allow the monitoring of the aggregate formation. In both cases, the appearance of these bands involves a nonreversible path in protein folding. It has been suggested that a difference in the ordered structures involves an increasing in band intensity. This change can be the origin in variations on the 2DCOS maps. The synchronous map gives an overall idea of the process involved. The asynchronous is more informative because reflects the kinetic changes produced. The outcome of both processes, amorphous or ordered is that 2DCOS can provide a further insight to the knowledge of the kinetic processes giving rise to aggregated structures. This outcome could consist on the order in which the different secondary structures are prone to form the aggregates.

Keywords: Infrared, protein folding, protein misfolding, structure, 2DCOS, band-fitting, Cell viability, protein metabolism, endoplasmic reticulum, cell control, protein synthesis, tridimensional structure, non-active aggregates, Infrared spectroscopy, 2DCOS maps, synchronous map