Structural and biochemical insights into Zn²⁺-bound EF-hand proteins, EFhd1 and EFhd2

Abstract

EF-hand proteins, which contain a Ca2+-binding EF-hand motif, are involved in regulating diverse cellular functions. Ca2+ binding induces conformational changes that modulate the activities of EF-hand proteins. Moreover, these proteins occasionally modify their activities by coordinating metals other than Ca2+, including Mg2+, Pb2+ and Zn2+, within their EF-hands. EFhd1 and EFhd2 are homologous EF-hand proteins with similar structures. Although separately localized within cells, both are actin-binding proteins that modulate F-actin rearrangement through Ca2+-independent actin-binding and Ca2+-dependent actin-bundling activity. Although Ca2+ is known to affect the activities of EFhd1 and EFhd2, it is not known whether their actin-related activities are affected by other metals. Here, the crystal structures of the EFhd1 and EFhd2 core domains coordinating Zn2+ ions within their EF-hands are reported. The presence of Zn2+ within EFhd1 and EFhd2 was confirmed by analyzing anomalous signals and the difference between anomalous signals using data collected at the peak positions as well as low-energy remote positions at the Zn K-edge. EFhd1 and EFhd2 were also found to exhibit Zn2+-independent actin-binding and Zn2+-dependent actin-bundling activity. This suggests the actin-related activities of EFhd1 and EFhd2 could be regulated by Zn2+ as well as Ca2+.

Recognition of Aedes aegypti Mosquito Saliva Protein LTRIN by the Human Receptor LTβR for Controlling the Immune Response

“…Further, the Ca 2+ binding ability of ∆LTRIN is confirmed by isothermal titration calorimetry (ITC) with K D value 27.3 × 10 −6 ± 9.43 × 10 −6 M (Supplementary Figure S2c). The Ca 2+ binding EF-hand motif is also known to accommodate other divalent ions such as Mg 2+ and Zn 2+ [40,41]. We also performed ITC experiments with these two ions.…”