Eur. Phys. J. E (2013) 36: 62
https://doi.org/10.1140/epje/i2013-13062-7

Regular Article

Protein packing defects “heat up” interfacial water

¹ Sección Fisicoquímica, INQUISUR-UNS-CONICET-Departamento de Química, Universidad Nacional del Sur, Avda. Alem 1253, 8000, Bahía Blanca, Argentina
² Instituto Argentino de Matemática “Alberto P. Calderón”, CONICET (National Research Council), Saavedra 15, 1083, Buenos Aires, Argentina
³ Collegium Basilea, Institute for Advanced Study, Hochstrasse 51, CH4053, Basel, Switzerland

^* e-mail: mbsierra@uns.edu.ar
^** e-mail: appignan@criba.edu.ar

Received: 24 November 2012
Revised: 5 April 2013
Accepted: 22 May 2013
Published online: 25 June 2013

Abstract

Ligands must displace water molecules from their corresponding protein surface binding site during association. Thus, protein binding sites are expected to be surrounded by non-tightly-bound, easily removable water molecules. In turn, the existence of packing defects at protein binding sites has been also established. At such structural motifs, named dehydrons, the protein backbone is exposed to the solvent since the intramolecular interactions are incompletely wrapped by non-polar groups. Hence, dehydrons are sticky since they depend on additional intermolecular wrapping in order to properly protect the structure from water attack. Thus, a picture of protein binding is emerging wherein binding sites should be both dehydrons rich and surrounded by easily removable water. In this work we shall indeed confirm such a link between structure and dynamics by showing the existence of a firm correlation between the degree of underwrapping of the protein chain and the mobility of the corresponding hydration water molecules. In other words, we shall show that protein packing defects promote their local dehydration, thus producing a region of “hot” interfacial water which might be easily removed by a ligand upon association.