Angiotensin-I converting enzyme 2 (ACE2) is the receptor for severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV). A previous study indicated that ACE2 from a horseshoe bat, the host of a highly related SARS-like coronavirus, could not function as a receptor for SARSCoV. Here, we demonstrate that a 3 aa change from SHE (aa 40-42) to FYQ was sufficient to convert the bat ACE2 into a fully functional receptor for SARS-CoV. We further demonstrate that an ACE2 molecule from a fruit bat, which contains the FYQ motif, was able to support SARS-CoV infection, indicating a potentially much wider host range for SARS-CoV-related viruses among different bat populations.Severe acute respiratory syndrome (SARS) represents one of the most severe epidemic infections of the 21st century, exacerbated by the fact that the causative agent was totally unknown at the time of the outbreaks Peiris et al., 2004). Since the discovery of the SARS coronavirus (SARS-CoV) as the aetiological agent of the disease (Drosten et al., 2003;Ksiazek et al., 2003;, there has been tremendous progress made in almost every aspect of SARS-related research. One of the more significant achievements was the identification of the angiotensin-I converting enzyme 2 (ACE2) as the cellular receptor for SARS-CoV . This discovery opened up new opportunities in the search for novel antiviral drugs as part of the overall countermeasure strategy to aid in the control of any future outbreaks (Han et al., 2006;Kuhn et al., 2007).In comparison, the progress in elucidating the origin of SARS-CoV was relatively slow and less straightforward. Although it was recognized very early during the outbreaks that SARS-CoV was most probably a virus of animal origin and that the virus entered the human population as a result of a spillover event(s), the exact reservoir species of the SARS-CoV and the path of the spillover event remain unknown Normile & Enserink, 2003;Wang & Eaton, 2007;Wang et al., 2006). However, it is well established that Himalayan palm civets (Paguma larvata) played a key role as an intermediate adapting/ amplifying host for the introduction of SARS-CoV into the human population Wang et al., 2006).The search for the origin of SARS-CoV was boosted when genetically similar SARS-like coronaviruses (SL-CoVs) were discovered in horseshoe bats in the genus Rhinolophus by two independent groups in Hong Kong and mainland China (Lau et al., 2005;Li et al., 2005b). SLCoVs and SARS-CoVs share identical genome organization and very high sequence identities. However, a closer examination revealed that the N-terminal region of the spike protein (S), known to be responsible for receptor binding in CoVs, displayed major sequence differences between the two groups of viruses (Li et al., 2005b). It was later shown that the S protein of the SL-CoV isolated from the horseshoe bat Rhinolophus pearsonii was unable to use the ACE2 molecule, either from human or R. pearsonii, as the entry receptor. The cellular molecule(s) that functions as the receptor for SL-CoVs is still ...