Crystal structure of ribonuclease T1 carboxymethylated at Glu58 in complex with 2'-GMP.Ishikawa, K., Suzuki, E., Tanokura, M., Takahashi, K.
(1996) Biochemistry 35: 8329-8334
- PubMed: 8679590
- DOI: 10.1021/bi960493d
- Primary Citation of Related Structures:
- PubMed Abstract:
- Three-Dimensional Structure of the Ternary Complex between Ribonuclease T1, Guanosine 3',5'-Bisphosphate and Inorganic Phosphate at 0.19 Nm Resolution
Lenz, A., Choe, H.W., Granzin, J., Heinemann, U., Saenger, W.
(1993) Eur J Biochem 211: 311
- X-Ray Analysis of Cubic Crystals of the Complex Formed between Ribonuclease T1 and Guanosine-3',5'-Bisphosphate
Lenz, A., Heinemann, U., Maslowska, M., Saenger, W.
(1991) Acta Crystallogr B 47: 521
- Specific Protein-Nucleic Acid Recognition in Ribonuclease T1-2'-Guanylic Acid Complex: An X-Ray Study
Heinemann, U., Saenger, W.
(1982) Nature 299: 27
The carboxymethylation of RNase T1 at the gamma-carboxyl group of Glu58 leads to a complete loss of the enzymatic activity while it retains substrate-binding ability. Accompanying the carboxymethylation, RNase T1 undergoes a remarkable thermal stabilization of 9 degrees C in the melting temperature (Tm) ...
The carboxymethylation of RNase T1 at the gamma-carboxyl group of Glu58 leads to a complete loss of the enzymatic activity while it retains substrate-binding ability. Accompanying the carboxymethylation, RNase T1 undergoes a remarkable thermal stabilization of 9 degrees C in the melting temperature (Tm). In order to clarify the inactivation and stabilization mechanisms of RNase T1 by carboxymethylation, the crystal structure of carboxymethylated RNase T1 (CM-RNase T1) complexed with 2'-GMP was determined at 1.8 A resolution. The structure, including 79 water molecules and two Na+, was refined to an R factor of 0.194 with 10 354 reflections > 1 sigma (F). The carboxyl group of CM-Glu58, which locates in the active site, occupies almost the same position as the phosphate group of 2'-GMP in the crystal structure of intact RNase T1.2'-GMP complex. Therefore, the phosphate group of 2'-GMP cannot locate in the active site but protrudes toward the solvent. This forces 2'-GMP to adopt an anti form, which contrasts with the syn form in the crystal of the intact RNase T1.2'-GMP complex. The inaccessibility of the phosphate group to the active site can account for the lack of the enzymatic activity in CM-RNase T1. One of the carboxyl oxygen atoms of CM-Glu58 forms two hydrogen bonds with the side-chains of Tyr38 and His40. These hydrogen bonds are considered to mainly contribute to the higher thermal stability of CM-RNase T1. Another carboxyl oxygen atoms of CM-Glu58 is situated nearby His40 and Arg77. This may provide additional electrostatic stabilization.
Central Research Laboratories, Ajinomoto Company, Inc., Kawasaki, Japan.