Purification and properties of the gamma-butyrobetaine-binding protein from an Agrobacterium sp.

A binding protein for gamma-butyrobetaine was purified from osmotic shock fluid of an Agrobacterium sp. It was a monomeric protein with an apparent molecular weight of 52,000 or 53,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, respectively. The isoelectric point was 4.3, as determined by isoelectric focusing. Amino acid analysis of the protein showed that Asx and Glx were predominant components and that the protein contained no cysteine. The dissociation constant of this protein for gamma-butyrobetaine was found to be 0.7 microM by equilibrium dialysis. Attempts to sequence the amino-terminal end with the Edman method failed, suggesting that this region of the protein is blocked.