Substitution of aspartic acid with glutamic acid increases the unfolding transition temperature of a protein.
Proteins from thermophiles are more stable than those from mesophiles. Several factors have been suggested as causes for this greater stability, but no general rule has been found. The amino acid composition of thermophile proteins indicates that the content of polar amino acids such as Asn, Gln, Ser, and Thr is lower, and that of charged amino acids such as Arg, Glu, and Lys is higher than in mesophile proteins. Among charged amino acids, however, the content of Asp is even lower in thermophile proteins than in mesophile proteins. To investigate the reasons for the lower occurrence of Asp compared to Glu in thermophile proteins, Glu was substituted with Asp in a hyperthermophile protein, MjTRX, and Asp was substituted with Glu in a mesophile protein, ETRX. Each substitution of Glu with Asp decreased the Tm of MjTRX by about 2 degrees C, while each substitution of Asp with Glu increased the Tm of ETRX by about 1.5 degrees C. The change of Tm destabilizes the MjTRX by 0.55 kcal/mol and stabilizes the ETRX by 0.45 kcal/mol in free energy.
Lee
Duck Yeon
DY
Biomedical Research Center, Korea Institute of Science and Technology, Cheongyang Box 131, Seoul 130-650, Republic of Korea.
Kim
Kyeong-Ae
KA
Yu
Yeon Gyu
YG
Kim
Key-Sun
KS
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001224:Aspartic Acid / Q000737:chemistry* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D003198:Computer Simulation; D019605:Euryarchaeota / Q000145:classification / Q000378:metabolism*; D018698:Glutamic Acid / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry*; D013045:Species Specificity; D013329:Structure-Activity Relationship; D013879:Thioredoxins / Q000737:chemistry* / Q000235:genetics; D044366:Transition Temperature
D001426:Bacterial Proteins; D011994:Recombinant Proteins; D001224:Aspartic Acid; D018698:Glutamic Acid; D013879:Thioredoxins