Sulfate-binding protein from Salmonella typhimurium: physical properties

Area of Science:

• Structural Biology
• Microbial Physiology
• Biochemistry

Background:

• Sulfate transport is vital for microbial metabolism.
• Salmonella typhimurium utilizes specific proteins for nutrient uptake.
• Understanding protein structure-function relationships is key to microbial physiology.

Purpose of the Study:

• To elucidate the physical and crystallographic properties of a sulfate-binding protein from Salmonella typhimurium.
• To investigate the structural basis of sulfate binding and transport.
• To determine the molecular characteristics influencing the protein's function.

Main Methods:

• X-ray diffraction for crystallographic analysis.
• Physical measurements including molecular weight and axial ratio determination.
• Spectroscopic techniques (light absorption, ORD, CD, fluorescence) and NMR for assessing physical properties.

Main Results:

• The protein exhibits a molecular weight of 32,000 and an axial ratio of 4:1, indicating a highly asymmetric, prolate ellipsoid shape.
• Crystals are elongate prisms, and X-ray diffraction data yield reflections to at least 2 angstroms spacing.
• The orthorhombic unit cell (P2(1)2(1)2(1)) dimensions are 40.8 x 47.5 x 136 angstroms, consistent with the observed molecular asymmetry.
• Sulfate binding minimally affected measured physical properties, suggesting structural stability.

Conclusions:

• The characterized protein is strongly implicated in sulfate transport in Salmonella typhimurium.
• Its asymmetric molecular structure is a key feature, likely facilitating its transport role.
• The protein's physical properties are largely independent of sulfate binding under the tested conditions.