Probing Protein Mechanics with Probing Protein Mechanics with Simulations and Molecular Dynamics Simulations and SingleSingle--Molecule ExperimentsMolecule Experiments

PRAC: The Computational Microscope PI: Emad Tajkhorshid Co-PIs: Rafael C. Bernardi, John E. Stone, and James C. Phillips

Rafael C. Bernardi Theoretical and Computational Group NIH Center for Macromolecular Modeling and Bioinformatics Beckman Institute for Advanced Science and Technology University of at Urbana-Champaign Urbana, IL

[email protected] www.ks.uiuc.edu/~rcbernardi What are we doing in Illinois?

Development of NAMD & VMD: • Available for Free; • One of the Most used Software in US Super Computer Centers;

Over 700 publications;

Prof. Emad Tajkhorshid Prof. Zan Luthey-Schulten Prof. Klaus Schulten Over 120k citations;

NIH Center for Macromolecular Modeling and Bioinformatics NSF Center for the of Living Cells

Rafael C. Bernardi www.ks.uiuc.edu/~rcbernardi Probing Protein Mechanics with Molecular Dynamics Simulations and Single-Molecule Experiments

in silico (Steered Molecular Dynamics) in vitro (AFM-based SMFS)

Prof. Klaus Schulten Prof. Hermann Gaub Beckman Institute LMU Munich, University of Illinois

Prof. Zaida Luthey-Schulten Prof. Michael Nash Department of Chemistry University of Basel, Switzerland University of Illinois

NIH Center for Macromolecular Modeling and Bioinformatics NCSA Combining in silico and in vitro Experiments Unraveling Molecular Mechanisms of Extreme Mechanostability in Proteins

Experimental Setup Computational Setup in vitro in silico Single-Molecule Force a Dockerins c Spectroscopy (SMFS) Steered Molecular X AFM Dynamics (SMD) Cohesins Coh ScaC cantilever Atomic Force Enzymes PEG

ScaA Microscope (AFM) CBM ScaE Coh Doc ScaB X Doc Protein Complex of Interest XMod

XMod-Doc:Coh XMod Force Xyn CttA CBM CBM X PEG Glass

R. flavefaciens Extension Cellulosic substrate ScaE surface b Rafael C. Bernardi www.ks.uiuc.edu/~rcbernardi

X-module Cohesin Dockerin Extreme Mechanostability in Bacterial Proteins

Cellulosomes Adhesins

Rafael C. Bernardi www.ks.uiuc.edu/~rcbernardi Cellulosomes are Used by Some Bacteria to Digest Plant Fiber

Cellulosomal organisms often live in a turbulent environment.

How Mechanically Stable are Cellulosomes?

RC Bernardi, et. al. Enhanced sampling techniques in molecular dynamics simulations of biological systems. BBA, 2015

Rafael C. Bernardi www.ks.uiuc.edu/~rcbernardi CohE:CttA

PDBid:4IU3

R. flavefaciens Rafael C. Bernardi www.ks.uiuc.edu/~rcbernardi Strongest Non-Covalent Bond Ever Found

Molecular Finger Trap Puzzle

KD = 20 nM About the same as a typical antibody–antigen

Rupture Under Force = 600-750 pN Antibody-antigen rupture at only ~60 pN

About half the rupture force of a covalent gold-thiol bond

C Schoeler, KH Malinowska, RC Bernardi, et. al. Ultrastable cellulosome-adhesion complex tightens under load. Nature Communications, 2014 C Schoeler, RC Bernardi, et. al. Mapping mechanical force propagation through biomolecular complexes. Nano Letters, 2015 M Scheurer, P Rodenkirch, M Siggel, RC Bernardi, et. al. PyContact: Rapid, customizable, and visual analysis of noncovalent interactions in MD simulations. Biophysical Journal, 2018 Rafael C. Bernardi www.ks.uiuc.edu/~rcbernardi Can we use simulations to engineer modified cellulosomal proteins?

Rafael C. Bernardi www.ks.uiuc.edu/~rcbernardi Are the cohesins in a scaffold different?

Bridging Cohesins are Stronger than Hanging Cohesins. Proposed by Valbuena, et. al. PNAS 2009