We read with great interest the recent PlosONE publication of Ke, et al. reporting the 1.9 angstrom structure of SHV-1 beta-lactamase with Penem 1 inhibitor. The structure reveals that the C7 R group of the inhibitor intermediate is in an R configuration. In addition, compared to a related inhibitor (Penem 2 in this reference), there is a rotation about the serine ester bond linking the inhibitor to the protein, with movement of the Y105 residue to avoid a steric clash with the carboxylate group of the inhibitor (Figure 3B). We had previously reported on the catalyic efficiency and inhibitor resistance properties of Y105 substituted SHV-1 (Li, et al. Antimicrob. Agents Chemother. 2012, 56(11):5678, published ahead of print 20 August 2012) and noted that Penem 1 remained active against Y105 variants of SHV-1 despite previous models of related inhibitors with SHV-1. Our model of the thiazepine intermediate revealed, similar to the crystal structure, an R configuration at C7, and a rotation about the serine ester bond with movement of the Y105 group. The C7 ring substituent is thus 6.5 A away from the Y105 and makes no interactions with this sidechain. This explains the lack of effect of Y105 mutations on the inhibitory capacity of the Penem 1 inhibitor. It also points out how far molecular modeling has come in accurate structure predictions compared to an earlier model of SHV-1 with the Penem 1 inhibitor (Mansour, et al., ChemMedChem 2007, 2:1713.).