Structural and Functional Analysis of the DNA Binding Protein Saci_0101 from the Hyperthermophile Sulfolobus acidocaldarius

• Main Authors: Dong-Lin Hsieh, 謝東霖
• Other Authors: Chin-Yu Chen
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/32290614948984715230

碩士 === 國立中央大學 === 生命科學系 === 104 === Saci_0101 is commonly believed to be a histone-like protein involved in genomic DNA compaction from Sulfolobus acidocaldarius. Here, to obtain a detailed understanding of its architectural properties, we present two crystal structures of wild type Saci_0101 in different crystal forms at 1.30 Å and 1.40 Å resolution, respectively. The overall crystal structures of both wild type are similar with the homologues of Sso7c4 in S. solfataricus and have a homodimeric DNA-binding fold forming a swapped -loop- ‘Ying-Yang’ topology. The crystal structure of its single mutant, I20M also has been solved at 1.55 Å resolution. Interestingly, the single mutation by replacing Ile with Met leads to the shortening of 1 helix and even makes the mutant structure much more static than the wild type, proved by the very small B-factor of 14 in I20M structure. In fluorescence polarization study, wild type Saci_0101 binds to a 20-bp double-stranded DNA with a binding affinity of 1.23 ± 0.19 M, which is close to other nonspecific dsDNA-binding proteins in Sulfolobus species. The EM studies show Saci_0101 may shape DNA as a wrapper and a briddger, which suggests Saci_0101 play a role in DNA packaging and duplex stabilization at the elevated growth temperatures.