title: Intrinsically disordered regions may lower the hydration free energy in proteins: a case study of nudix hydrolase in the bacterium Deinococcus radiodurans.
abstract: The proteome of the radiation- and desiccation-resistant bacterium D. radiodurans features a group of proteins that contain significant intrinsically disordered regions that are not present in non-extremophile homologues. Interestingly, this group includes a number of housekeeping and repair proteins such as DNA polymerase III, nudix hydrolase and rotamase. Here, we focus on a member of the nudix hydrolase family from D. radiodurans possessing low-complexity N- and C-terminal tails, which exhibit sequence signatures of intrinsic disorder and have unknown function. The enzyme catalyzes the hydrolysis of oxidatively damaged and mutagenic nucleotides, and it is thought to play an important role in D. radiodurans during the recovery phase after exposure to ionizing radiation or desiccation. We use molecular dynamics simulations to study the dynamics of the protein, and study its hydration free energy using the GB/SA formalism. We show that the presence of disordered tails significantly decreases the hydration free energy of the whole protein. We hypothesize that the tails increase the chances of the protein to be located in the remaining water patches in the desiccated cell, where it is protected from the desiccation effects and can function normally. We extrapolate this to other intrinsically disordered regions in proteins, and propose a novel function for them: intrinsically disordered regions increase the "surface-properties" of the folded domains they are attached to, making them on the whole more hydrophilic and potentially influencing, in this way, their localization and cellular activity.
authors.affiliation: Mediterranean Institute for Life Sciences, Split, Croatia.
authors.forename: Omar
authors.initials: O
authors.lastname: Awile
authors.forename: Anita
authors.initials: A
authors.lastname: Krisko
authors.forename: Ivo F
authors.initials: IF
authors.lastname: Sbalzarini
authors.forename: Bojan
authors.initials: B
authors.lastname: Zagrovic
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D034301:Deinococcus / Q000201:enzymology*; D003890:Desiccation; D057927:Hydrophobic and Hydrophilic Interactions; D056004:Molecular Dynamics Simulation; D011487:Protein Conformation; D011755:Pyrophosphatases / Q000737:chemistry*; D020539:Sequence Analysis, Protein; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water / Q000737:chemistry; D000096964:Nudix Hydrolases
chemical_list: D001426:Bacterial Proteins; D011755:Pyrophosphatases; D014867:Water; D000096964:Nudix Hydrolases