The severe acute respiratory syndrome (SARS) coronavirus (CoV) identified in 
2003 has infected ∼8000 people worldwide, killing nearly 10% of them. The 
infection of target cells by the SARS CoV is mediated through the interaction of 
the viral Spike (S) protein (1255 amino acids) and its cellular receptor, 
angiotensin-converting enzyme 2 (ACE2). The SARS CoV receptor-binding domain 
(amino acids N318-T509 of S protein) harbors an extended excursion along its 
periphery that contacts ACE2 and is designated the receptor-binding motif (RBM, 
amino acids S432-T486). In addition, the RBM is a major antigenic determinant, 
able to elicit production of neutralizing antibodies. Hence, the role of the RBM 
is a bi-functional bioactive surface that can be demonstrated by antibodies such 
as the neutralizing human anti-SARS monoclonal antibody (mAb) 80R which targets 
the RBM and competes with the ACE2 receptor for binding. Here, we employ 
phage-display peptide-libraries to reconstitute a functional RBM. This is 
achieved by generating a vast collection of candidate RBM peptides that present 
a diversity of conformations. Screening such 'Conformer Libraries' with 
corresponding ligands has produced short RBM constructs (ca. 40 amino acids) 
that can bind both the ACE2 receptor and the neutralizing mAb 80R.