An artificially constructed dimer through deformation of a short zinc-binding loop

Publication date: Available online 6 November 2017 Source:Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics Author(s): Jimin Park, Mi-Sun Kim, Keehyung Joo, Jooyoung Lee, Dong Hae Shin We have analyzed the crystal structure of the dimeric form of d-glycero-d-manno-heptose-1,7-bisphosphate phosphatase from Burkholderia thailandensis (BtGmhB), catalyzing the removal of the phosphate at the 7 position of d-glycero-d-manno-heptose-1,7-bisphosphate. The crystal structure of BtGmhB revealed a dimeric form caused by a disruption of a short zinc-binding loop. The dimeric BtGmhB structure was induced by triggering the loss of Zn2+ via the protonation of cysteine residues at pH 4.8 of the crystallization condition. Similarly, the addition of EDTA also causes the dimerization of BtGmhB. It appears there are two dimeric forms in solution with and without the disulfide bridge mediated by Cys95. The disulfide-free dimer produced by the loss of Zn2+ in the short zinc-binding is further converted to a stable disulfide-bonded dimer in vitro. Though the two dimeric forms are reversible, both of them are inactive due to a deformation of the active site. Single and triple mutant experiments confirmed the presence of two dimeric forms in vitro. Phosphatase assay results showed that only a zinc-bound monomeric form contains catalytic activity in contrast to the inactive zinc-free dimeric forms. The monomer-to-dimer transition caused by the loss of Zn2+ observed in this study is ...
Source: Biochimica et Biophysica Acta (BBA) Proteins and Proteomics - Category: Biochemistry Source Type: research