Question

Halophilic bacteria have been developed to live in a very salty environment, e.g. Dead Sea. The most important salts in the Dead Sea are MgCl2 (1.83 M), NaCl (1.78 M), CaCl2
(0.44 M) and KCl (0.20 M). Typical for halophilic organisms is that their proteins have a much larger (negative) net charge than proteins in organisms that live at normal salinity.

(a) Explain why the proteins of halophilic organisms need a large net charge in order for the proteins not to aggregate with each other in the salt environment.
(b) Placing a halophilic protein in a low salt aqueous solution usually denatures (ie, folds out). Estimate how much ∆_unfoldG changes for a typical halophilic protein with a radius of 15 Å as it moves from the Dead Sea to pure water at 25◦C. Assume that the surface charge density of the protein is −1e per 1000 Ų.
(c) What conclusion can you draw about the stability of halophilic proteins in aqueous solution at normal salinity?

Answer 1

(a)Halophilic proteins having high negative charge to prevent them from aggregating and collapsing and such proteins appear to be independent irrespective of the salt concentration and does not interfere with the electrostatic interactions of the proteins in which they bind to large amounts of salts as they have large number of acidic amino acidsan the surface of the protein

(b)unfloding takes place to greater extent because the halophiles cannot tolerate low salt or pure environments which causes protein unfloding and collapsing

(c)at normal salinity protein unfloding occurs as halophiles have high net negavtive charge and they will not be stable