Most biomolecules become functional and bioactive by forming protein
complexes through interaction with ligands that are diverse in size,
shape, and physicochemical properties. In the complex biological milieu,
the interaction is ligand-specific, driven by molecular sensing and
recognition of a binding interface localized within a protein structure.
Mapping interfaces of protein complexes is a highly sought area of
research as it delivers fundamental insights into proteomes and
pathology and hence strategies for therapeutics. While X-ray
crystallography and electron microscopy still serve as a gold standard
for structural elucidation of protein complexes, artificial and static
analytic nature thereof often results in a non-native interface that
otherwise might be negligible or non-existent in biological environment.
In recent years, the mass spectrometry-coupled approaches, chemical
crosslinking (CLMS) and hydrogen-deuterium exchange (HDMS), have become
valuable analytic complements to traditional techniques. These methods
explicitly identify hot residues and motifs embedded in binding
interfaces, in particular, for which the interaction is predominantly
dynamic, transient, and/or caused by an intrinsically disordered
domain. Here we review the principal role of CLMS and HDMS in protein
structural biology with a particular emphasis on the contribution of
recent examples to exploring biological interfaces. In addition, we
describe recent studies that utilized these methods to expand our
understanding of protein complex formation and related biological
processes and to increase probability of structure-based drug design.