Structure of the S100A4/myosin-IIA complex

Abstract

BackgroundS100A4, a member of the S100 family of Ca2+-binding proteins, modulates the motility of both non-transformed and cancer cells by regulating the localization and stability of cellular protrusions. Biochemical studies have demonstrated that S100A4 binds to the C-terminal end of the myosin-IIA heavy chain coiled-coil and disassembles myosin-IIA filaments; however, the mechanism by which S100A4 mediates myosin-IIA depolymerization is not well understood.ResultsWe determined the X-ray crystal structure of the S100A4Δ8C/MIIA1908-1923 peptide complex, which showed an asymmetric binding mode for the myosin-IIA peptide across the S100A4 dimer interface. This asymmetric binding mode was confirmed in NMR studies using a spin-labeled myosin-IIA peptide. In addition, our NMR data indicate that S100A4Δ8C binds the MIIA1908-1923 peptide in an orientation very similar to that observed for wild-type S100A4. Studies of complex formation using a longer, dimeric myosin-IIA construct demonstrated that S100A4 binding dissociates the two myosin-IIA polypeptide chains to form a complex composed of one S100A4 dimer and a single myosin-IIA polypeptide chain. This interaction is mediated, in part, by the instability of the region of the myosin-IIA coiled-coil encompassing the S100A4 binding site.ConclusionThe structure of the S100A4/MIIA1908-1923 peptide complex has revealed the overall architecture of this assembly and the detailed atomic interactions that mediate S100A4 binding to the myosin-IIA heavy chain. These structural studies support the idea that residues 1908–1923 of the myosin-IIA heavy chain represent a core sequence for the S100A4/myosin-IIA complex. In addition, biophysical studies suggest that structural fluctuations within the myosin-IIA coiled-coil may facilitate S100A4 docking onto a single myosin-IIA polypeptide chain.

Multilevel Changes in Protein Dynamics upon Complex Formation of the Calcium‐Loaded S100A4 with a Nonmuscle Myosin IIA Tail Fragment

“…[14,27,43] The 1 H, 15 NH SQC spectrum of S100A4dCh as well-dispersed resonances, as expectedf or af olded protein. ACterminally 13 residues truncated form of Ca 2 + -bound S100A4 (S100A4dC) wasu sed, in order to avoid the aggregation tendency of full-length S100A4.P revious studies indicated that MPT binding is not affectedb yt his C-terminal truncation.…”

“…[9][10][11][12][13][14] All the distinctive structural elements characteristic for S100 proteins are present:t he pseudo-EF hand near the Nterminus (formed by helicesH 1a nd H2, which surround loop L1), ac onnecting "hinge" (L2) and the canonical EF-handc lose to the Cterminus (L3 loop flankedb y helices H3 and H4). [9][10][11][12][13][14] All the distinctive structural elements characteristic for S100 proteins are present:t he pseudo-EF hand near the Nterminus (formed by helicesH 1a nd H2, which surround loop L1), ac onnecting "hinge" (L2) and the canonical EF-handc lose to the Cterminus (L3 loop flankedb y helices H3 and H4).…”

“…[20] Interaction of S100A4 with nonmuscle myosin IIA (NMIIA)i s thought to be associated with increased cell migration of metastatic cells. [14,[25][26][27] The S100A4-binding region of NMIIA comprises the Cterminus of the coiled-coil dimer and part of the nonhelical tailpiece. [21,22] S100A4 colocalizes with NMIIA at the leading edge of migrating cells and regulates directional motilityt hrough direct interaction with NMIIA.…”

The C-Terminal Random Coil Region Tunes the Ca2+-Binding Affinity of S100A4 through Conformational Activation

“…Therefore we solved the crystal structure of Ca 2+ -saturated Δ13 mutant in complex with MPT peptide (Supporting information, Figure S6, Table S4), which apart from some differences observed (Supporting information, Figure S7), essentially confirmed the asymmetric binding mode of MPT observed in complexes of the full length protein [7], [8] and Δ8 C-terminal truncated mutant [9].…”

S100 proteins in cancer

“…As a consequence, target binding is typically Ca 2+ -dependent. Importantly, the three-dimensional structures of S100–target complexes have revealed that individual family members exhibit distinct modes of target recognition owing, in part, to differences in surface geometries, hydrophobic residue distribution and charge density 25 . In addition, some family members undergo a variety of post-translational modifications, such as oxidative modification and sumoylation, which can modulate S100–target complex formation and/or intracellular localization 26–29 .…”