Two exposed amino acid residues confer thermostability on a cold shock protein.
Thermophilic organisms produce proteins of exceptional stability. To understand protein thermostability at the molecular level we studied a pair of cold shock proteins, one of mesophilic and one of thermophilic origin, by systematic mutagenesis. Although the two proteins differ in sequence at 12 positions, two surface-exposed residues are responsible for the increase in stability of the thermophilic protein (by 15.8 kJ mol-1 at 70 degrees C). 11.5 kJ mol-1 originate from a predominantly electrostatic contribution of Arg 3 and 5.2 kJ mol-1 from hydrophobic interactions of Leu 66 at the carboxy terminus. The mesophilic protein could be converted to a highly thermostable form by changing the Glu residues at positions 3 and 66 to Arg and Leu, respectively. The variation of surface residues may thus provide a simple and powerful approach for increasing the thermostability of a protein.
Perl
D
D
Biochemisches Laboratorium, Universität Bayreuth, D-95440 Bayreuth, Germany.
Mueller
U
U
Heinemann
U
U
Schmid
F X
FX
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001407:Bacillus / Q000737:chemistry*; D001412:Bacillus subtilis / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D016415:Sequence Alignment; D055672:Static Electricity; D013696:Temperature; D013816:Thermodynamics
D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; C407094:cold shock protein, Bacillus; C077188:cold-shock protein CspB, Bacteria