Site-directed mutagenesis was used to obtain seven variants of tryptic fragment of bovine liver cytochrome bs (cyt bs), in which the negatively charged residues around the heme exposed edge of cyt bs were replaced by hydropho-bic amino acid alanine. Double-site mutants, triple-site mutants and even quadruple-site mutants were obtained. DNA sequencing and molecular weight measurements of the mutant proteins both confirmed that these site-directed muta-genesises were successfully performed. Spectroelectrochem-istry of these mutant proteins revealed that the apparent redox potentials of these mutant proteins caused a positive shift of 2-10 mV. The global structure of these mutant proteins did not show much difference from that of the wild type cyt bs, providing a solid base for the further study on the roles of the proteins’ surface charges.
WANG Yunhua, WANG Wenhu, LU Junxia, REN Yi, GU Shaohua, XIE Yi & HUANG Zhongxian1. Chemical Biology Lab, Department of Chemistry, Fudan University, Shanghai 200433, China
The current development in the intramolecular aromatic-ring stacking interactions in the complexes with compositions of DNA and heteroaromatic N-bases has been reviewed to a great extent, especially the significant contributions in several important systems about ternary mixed-ligand complexes, including nucleotide-metal ion-po-lyaromatic amine, amino acid-metal ion-polyaromatic amine, nucleotide-metal ion-pyridine-like aromatic amine, nucleo-tide-metal ion-amino acid, nucleotide-metal ion-nucleic acid base, nucleic acid base-metal ion, and the important factors affecting the intramolecular aromatic-ring stacking interac-tions in the complexes. Based on the study of stacking inter-action in the complexes, the mechanism of interaction be-tween DNA molecules and complexes of heteroaromatic N-bases has been established, which is crucial for the design and synthesis of the complexes acting as molecular devices of DNA.
Jl Liangnian & LE XueyiDepartment of Chemistry, Key Laboratory for the Gene Engineering of the Ministry of Education of China, and State Key Laboratory of Ultrafast Laser Spectroscopy, Zhongshan University, Guangzhou 510275, China
