SARS-CoV-2(5) information(5) X-ray diffraction(3) X-ray data collection(3) polyproteins(3) protonation state(3) inactive(3) Proteins(3) mechanism(3) cysteine protease(3) Cys145(3) neutron diffraction(3) functional(3) pp1a(3) enzyme(3) catalytic site(3) replication of SARS-CoV-2(3) described(3) catalytic(3) X-ray(3) 3CL(3) M pro(3) His41(3) 3CL Mpro(3) determine(3) residue(3) catalytic dyad(3) pp1ab(3) collected(3) cleavage(3)