Molecular Dynamics Simulation Study on Allosteric Regulation of CD44-Hyaluronan Binding as a Force Sensing Mechanism.

CD44 protein exists on surfaces of a variety of human cells, acts as a receptor for the hyaluronan (HA) molecule, and mediates cell adhesion via the HA binding in leukocyte trafficking, cell rolling, and so on. The molecular structures of both CD44 and HA are well known, and the previous work shows that the external-mechanical force induces the partially disordered (PD) conformation from the ordered (O) conformation of CD44. The PD conformation has the higher HA affinity compared to the O conformation.

Intra-electron transfer induced by protonation in copper-containing nitrite reductase.

The inter- and intra-electron and proton transfers in the nitrite reduction of copper-containing nitrite reductase (CuNiR) were investigated by using the QM/MM method with the calculational models containing type 1 (T1) and type 2 (T2) Cu sites. The electron transfer from the outer electron donor protein to the T1 Cu site occurred both before and after nitrite binding, and nitrite binding lowered the reduction potential of the Cu T1 site. The protonation of catalytic His244 subsequent to nitrite binding and T1 Cu reduction induced partial intra-electron transfer from T1 to T2 Cu sites.