A dynamic loop provides dual control over the catalytic and membrane binding activity of a bacterial serine hydrolase

Publication date: September 2018Source: Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics, Volume 1866, Issue 9Author(s): Mackenzie A. Smith, Whitney K. Phillips, Perry L. Rabin, R. Jeremy JohnsonAbstractThe bacterial acyl protein thioesterase (APT) homologue FTT258 from the gram-negative pathogen Francisella tularensis exists in equilibrium between a closed and open state. Interconversion between these two states is dependent on structural rearrangement of a dynamic loop overlapping its active site. The dynamics and structural properties of this loop provide a simple model for how the catalytic activity of FTT258 could be spatiotemporally regulated within the cell. Herein, we characterized the dual roles of this dynamic loop in controlling its catalytic and membrane binding activity. Using a comprehensive library of loop variants, we determined the relative importance of each residue in the loop to these two biological functions. For the catalytic activity, a centrally located tryptophan residue (Trp66) was essential, with the resulting alanine variant showing complete ablation of enzyme activity. Detailed analysis of Trp66 showed that its hydrophobicity in combination with spatial arrangement defined its essential role in catalysis. Substitution of other loop residues congregated along the N-terminal side of the loop also significantly impacted catalytic activity, indicating a critical role for this loop in controlling catalytic activity. For membrane binding, t...
Source: Biochimica et Biophysica Acta (BBA) Proteins and Proteomics - Category: Biochemistry Source Type: research