Felix's paper on Structural and Biophysical Insights into SPINK1 Bound to Human Cationic Trypsin is published

Figure 1: Biophysical characterization of the SPINK1–TRY1 interaction. (A) Schechter and Berger nomenclature. (B) Size-exclusion chromatograms of purified SPINK1 WT (yellow), TRY1 p.S200A (cyan) and complex (black). (C) 16% tricine SDS–PAGE of purified TRY1 p.S200A–SPINK1 WT complex, TRY1 p.S200A and SPINK1 WT. (D) Michaelis–Menten kinetics of L-BAPA substrate with TRY1. Error bars represent standard deviations of three independent experiments. Km and kcat values represent fitted values and their standard error. (E) Trypsin activity assay at varying SPINK1 concentrations fitted with Morrison’s quadratic equation. Error bars represent standard deviations of three independent experiments. (F) Surface plasmon resonance single-cycle kinetic of the TRY1 p.S200A—SPINK1 WT or (G) p.N34S interaction fitted with a 1:1 Langmuir interaction model. (H) Isothermal titration calorimetry of the TRY1 p.S200A–SPINK1 WT or (I) p.N34S interaction fitted with a 1:1 binding site model. (J) Summary of equilibrium, kinetic and thermodynamic data. Ki values represent fitted values ± standard errors, while SPR and ITC data are reported as mean ± SD of at least three independent experiments.
Figure 2: Structure and superposition of TRY1 p.S200A–SPINK1 complexes. The black arrow indicates the position of the p.N34S mutation site. (A) Structures and superposition of TRY1 p.S200A (cyan) in complex with SPINK1 WT (yellow) or p.N34S (pink). Sulfate ions are shown as spheres and are colored according to their atom type. (B) Binding interface of SPINK1 p.N34S. Due to their similarity, the binding interface of SPINK1 WT was omitted but can be seen in Supplementary Figure S1. (C) SPINK1 WT in complex with TRY1 colored by B-factors.
Figure 3: Interactions between TRY1 p.S200A (cyan) and SPINK1 p.N34S (pink). (A) Lys41 in SPINK1 interacts with the specificity determining Asp194 in TRY1. (B) Asn56 in SPINK1 stabilizes the binding loop by hydrogen bonding with Thr40 and Ile42. (C) Tyr33 in SPINK1 forms a cation—pi bond with Arg101 in TRY1 and is hence pulled outward. (D) Catalytic triad of the TRY1 p.S200A–SPINK1 complex (cyan). The 2Fo–Fc density map is shown at 1.6 Å around the residues of the catalytic triad and is contoured at 1.5 σ. In the complex structure His63 is rotated toward the sulfate ion and out of the productive catalytic triad arrangement. (E) Sequence conservation of the Kazal 1 family displayed by an HMM logo generated in Skylign [35]. Amino acid letter height is calculated based on the information content above background expressed in bits.

First crystal structure of SPINK1 bound to human cationic trypsin for WT and N34S mutant ...

Felix's paper on Structural and Biophysical Insights into SPINK1 Bound to Human Cationic Trypsin is published in International Journal of Molecular Sciences. Congratulations Felix!

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