Structural Flexibility of Peripheral Loops and Extended C-terminal Domain of Short Length Substrate Binding Protein from Rhodothermus marinus

Data of radiation damage on selenomethionine-substituted single-domain substrate-binding protein

Radiation damage is an inherent issue in X-ray crystallography. It not only damages macromolecular crystals, which lowers the quality of the diffraction intensity, but results in inaccurate structural information. Among the various types of radiation damage, little is known regarding the damage to selenomethionine, an amino acid contained in some proteins. Recently, radiation damage to the selenomethionine-substituted single-domain substrate-binding domain from Rhodothermus marinus (SeMet-RmSBP) was investigated. Global and specific radiation damage from four datasets collected by repeatedly exposing a single RmSBP-SeMet crystal to X-rays were analyzed. The results indicated that the B-factor value of the selenium atom in selenomethionine was significantly increased compared with other atoms. To date, no images of radiation damage have been reported for selenomethionine-substituted proteins. Therefore, these data may be used to study radiation damage in macromolecular crystallography. This study provides insight into radiation damage associated with selenomethionine.

Structural and bioinformatics analysis of single-domain substrate-binding protein from Rhodothermus marinus

Substrate-binding proteins (SBPs) are key elements in determining the substrate specificity and high affinity of the ATP-binding cassette uptake system. A typical SBP has two domains that recognize substrates and are responsible for the specific substrate delivery. Conversely, in GenBank, genes for SBPs constituting a single domain SBP are often found in vicinity of a methyl-accepting chemotaxis protein gene. However, the molecular function and mechanism of single domain SBPs are not fully elucidated. To understand their molecular functions, we performed a crystallographic study of single domain SBP from Rhodothermus marinus (RmSBP). RmSBP crystals were soaked in solution containing NaBr or HgCl2 and their structures determined at 1.75 and 2.3 Å resolution, respectively. RmSBP soaked in NaBr exhibited disorder of the α2-helix, β5-to β6-strand loop, and C-terminus region, showing the structural dynamic region of RmSBP. RmSBP soaked in HgCl2 showed that Hg2+ bound to Cys145 located between the α5-and α6-helices. The structural properties of RmSBP were compared with those of single domain SBP homologs. These results will contribute to continued identification of the molecular function and mechanism of single domain SBPs.