Solid-State NMR and MD Study of the Structure of the Statherin Mutant SNa15 on Mineral Surfaces

Abstract

Elucidation of the structure and interactions of proteins at native mineral interfaces is key to understanding how biological systems regulate the formation of hard tissue structures. In addition, understanding how these same proteins interact with non-native mineral surfaces has important implications for the design of medical and dental implants, chromatographic supports, diagnostic tools, and a host of other applications. Here, we combine solid-state NMR spectroscopy, isotherm measurements, and molecular dynamics simulations to study how SNa15, a peptide derived from the hydroxyapatite (HAP) recognition domain of the biomineralization protein statherin, interacts with HAP, silica (SiO 2 ) and titania (TiO 2 ) mineral surfaces. Adsorption isotherms are used to characterize the binding affinity of SNa15 to HAP, SiO 2 , and TiO 2 . We also apply 1D 13 C CP MAS, 1D 15 N CP MAS, and 2D 13 C-13 C DARR experiments to SNa15 samples with uniformly 13 C-and 15 N-enriched residues to determine backbone and side-chain chemical shifts. Different computational tools, namely TALOS-N and molecular dynamics simulations, are used to deduce secondary structure from backbone and side-chain chemical shift data. Our results show that SNa15 adopts an α-helical conformation when adsorbed to HAP and TiO 2 , but the helix largely unravels upon adsorption to SiO 2 . Interactions with HAP are mediated in general by acidic and some basic amino acids, although the specific amino acids involved in direct surface interaction vary with surface. The integrated experimental and computational approach used in this study is able to provide high-resolution insights into adsorption of proteins on interfaces.

Data-Driven Molecular Dynamics: A Multifaceted Challenge

“…In a similar biological context, metadynamic metainference and NMR chemical shifts were exploited by Hultqvist et al to get insights into the interaction of the two disordered proteins CID and NCBD [143]. Backbone chemical shifts were also used by Buckle et al to investigate the interaction of the SNa15 peptide with non-native mineral surfaces [144]. Finally, concerning NMR, RDC data were employed in the metainference framework by Weber and coworkers to study the conformational space accessible to the LC protein [145].…”

Structural Biology of Calcium Phosphate Nanoclusters Sequestered by Phosphoproteins

“…The CaP-SLiMs in Table 1 do not appear to contain or flank any of the recognized motifs associated with binding phosphate anions such as anion nests or P-loops containing a basic residue (GXXXXGK(S,T)) [51][52][53]. The involvement of basic residues in the folding and binding of the N-terminal region of statherin to HA has been reported [54][55][56]. However, much more work is needed to investigate the potential co-binding to calcium and P i ions in the CaP by basic and acidic residues in or around the CaP-SLiM sequences.…”

“…The dentin matrix phosphoprotein 1 (DMP1) provides an example of the The interaction between the charged residues of IDPs and mineralized surfaces can, in some instances, induce or stabilize specific secondary structures. For example, the N-terminal region of statherin adopts an α-helical conformation upon absorption to mineral surfaces [54,55]. It has been suggested that this folding upon binding prevents further growth of HA by shielding the surface of the mineral phase from further addition of CaP [54].…”

“…For example, the N-terminal region of statherin adopts an α-helical conformation upon absorption to mineral surfaces [54,55]. It has been suggested that this folding upon binding prevents further growth of HA by shielding the surface of the mineral phase from further addition of CaP [54]. Folding-upon-binding events of IDPs may induce secondary structure elements that recruit other proteins involved in the biocalcification process to the mineral surface.…”

Anisotropy in Stable Conformations of Hydroxylate Ions between the {001} and {110} Planes of TiO2 Rutile Crystals for Glycolate, Lactate, and 2-Hydroxybutyrate Ions Studied by Metadynamics Method

“…1 Therefore, when considering the use of a particular additive to control crystal growth or morphology, it is important to investigate the thermodynamically stable conformations of the additives at various crystal surfaces. Although certain experimental techniques, such as infrared spectroscopy 2 and solid-state NMR, 3 can reveal information about the conformations of additives at wide crystal surfaces, the detailed conformations and dynamics of additives at specific planes of crystals grown in solution are difficult to determine experimentally.…”