Residue cluster additivity of thermodynamic stability in the hydrophobic core of mesophile vs. hyperthermophile rubredoxins.
The branched sidechain residues 24 and 33 in the hydrophobic core of rubredoxin differ between the Clostridium pasteurianum (Cp) and Pyrococcus furiosus (Pf) sequences. Their X-ray structures indicate that these two sidechains are in van der Waals contact with each other, while neither appears to significantly interact with the other nonconserved residues. The simultaneous interchange of residues 24 and 33 between the Cp and Pf rubredoxin sequences yield a complementary pair of hybrid proteins for which the sum of their thermodynamic stabilities equals that of the parental rubredoxins. The 1.2 kcal/mol change arising from this two residues interchange accounts for 21% of the differential thermodynamic stability between the mesophile and hyperthermophile proteins. The additional interchange of the sole nonconserved aromatic residue in the hydrophobic core yields a 0.78 kcal/mol deviation from thermodynamic additivity.
LeMaster
David M
DM
Wadsworth Center, New York State Department of Health, New York 12201-0509, USA.
Hernández
Griselda
G
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry; D003013:Clostridium / Q000737:chemistry; D018360:Crystallography, X-Ray; D057927:Hydrophobic and Hydrophilic Interactions; D011487:Protein Conformation; D020027:Pyrococcus furiosus / Q000737:chemistry; D012416:Rubredoxins / Q000737:chemistry*; D013045:Species Specificity; D013816:Thermodynamics
D001426:Bacterial Proteins; D012416:Rubredoxins