Papaleo_2011_Biopolymers_95_117

Most bacterial lipases bind one or more Ca(2)+ atoms at different locations and are a suitable case of study for investigating structural effects related to calcium binding, depletion, or mutation of calcium-binding sites. Generally Ca(2)+ in microbial lipases can play a crucial role in the stabilization of the whole three-dimensional structure by mediating long-range effects. It has been recently demonstrated that calcium binding influences thermal stability of Burkholderia glumae lipase (BGL) through the restriction of conformational plasticity of specific regions. Moreover, calcium depletion results in a highly cooperative protein unfolding, eliciting protein aggregation. To further shed light on molecular mechanisms and structural features connected to calcium binding in microbial lipases, we present a molecular dynamics investigation, based on multiple-replica approach at different temperatures, of BGL mutants targeting the calcium-binding site. It turns out that additional acidic residues, which are conserved in other microbial lipases, help in overcoming effects induced by mutation of D241 Ca(2)+-coordinating residue, upon rearrangements induced in the calcium binding site.