Functional Manipulation of a Calcium-binding Protein from Entamoeba histolytica Guided by Paramagnetic NMR

Abstract

Background: EhCaBP1 is one of the EF-hand calcium-binding proteins (CaBP) involved in various Ca 2ϩ signaling pathways. Results: Hydrophobic residues at the Ϫ4 position of the Ca 2ϩ -binding loop affects structure, Ca 2ϩ -binding properties, and cellular localization of EhCaBP1. Conclusion: The Y81F mutation in EhCaBP1 makes it more structured like CaM and TnC. Significance: Observed variations in the structures and cellular localization of the wt and mutant could have influence on their biological behavior.

EhRho1 regulates phagocytosis by modulating actin dynamics through EhFormin1 and EhProfilin1 inEntamoeba histolytica

“…EhRho1 was found in the supernatant fraction in presence of actin and GTP or GDP after cosedimentation, suggesting that EhRho1 did not directly bind F-actin unlike EhCaBP1, a known actin-binding protein present along with F-actin in the pellet fraction. In contrast, EhCaBP2, a close homologue of EhCaBP1, did not bind F-actin as expected (Rout et al, 2013; Figure S3b).…”

Machine learning-based modulation of Ca2+-binding affinity in EF-hand proteins and comparative structural insights into site-specific cooperative binding

“…The coordination of amino acid residues of EF-hand motifs with Ca 2+ occurred in a very conserved manner that forms a pentagonal bipyramidal geometry [5,7,9,10]. In most of the Ca 2+ binding proteins, including all CaMs, the residues in the Ca 2+ binding loop at positions +X(1 st residue of the loop), +Y(3 rd residue of the loop), +Z(5 th residue of the loop), -Y(7 th residue of the loop), -Z (9 th residue of the loop) and -X (12 th residue of the loop) coordinate with Ca 2+ directly, the 9 th (-Z) position residue does not coordinate the Ca 2+ directly, instead a water molecule involved in the coordination and 12 th position residue contributes donates two electron and complete the coordination sphere [7,[9][10][11][12].…”

“…Binding of Ca 2+ to CaM/CaM-like proteins, induces the conformational rearrangement which changes the energy landscape of these proteins, thereby interacts with many intracellular proteins [13]. The residue composition in the EF-hand binding loop is one of the major determinants, which dictate the Ca 2+ binding affinity of all CaBPs; other factors such as the conformational cost upon Ca 2+ binding, the EF-β-scaffold, cooperative binding, the physiological environment, also play crucial roles in the binding of the metal ion [5,12,14,15]. These factors lead to a wide range of Ca 2+ binding affinities, perhaps such diverse Ca 2+ binding affinity exhibited by CaBPs may allow them to perform variety of functions.…”