Amino acids conserved at the C-terminal half of the ribonuclease T2 family contribute to protein stability of the enzymes.
The ribonuclease MC1 (RNase MC1) from the seeds of the bitter gourd belongs to the RNase T2 family. We evaluated the contribution of 11 amino acids conserved in the RNase T2 family to protein folding of RNase MC1. Thermal unfolding experiments showed that substitution of Tyr(101), Phe(102), Ala(105), and Phe(190) resulted in a significant decrease in themostability; the T(m) values were 47-58 degrees C compared to that for the wild type (64 degrees C). Mutations of Pro(125), Gly(127), Gly(144), and Val(165) caused a moderate decrease in thermostability (T(m): 60-62 degrees C). In contrast, mutations of Asp(107) and Gly(173) did little effect on thermostability. The contribution of Tyr(101), Phe(102), Pro(125), and Gly(127) to protein stability was further corroborated by means of Gdn-HCl unfolding and protease digestions. Taken together, it appeared that Tyr(101), Phe(102), Ala(105), Pro(125), Gly(127), Gly(144), Leu(162), Val(165), and Phe(190) conserved in the RNase T2 family play an important role in the stability of the proteins.
Laboratory of Biochemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581, Japan.
Kazumi
K
Kimura
Tomoyuki
T
Numata
Yoshimitsu
Y
Kakuta
Makoto
M
Kimura
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000596:Amino Acids / Q000378:metabolism*; D004722:Endoribonucleases / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D029777:Momordica charantia / Q000201:enzymology; D009154:Mutation / Q000235:genetics; D017510:Protein Folding; D012260:Ribonucleases / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D000596:Amino Acids; D004722:Endoribonucleases; D012260:Ribonucleases; C413748:ribonuclease MC1; C022543:ribonuclease T(2)