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Center for Advanced Research in Biotechnology, University of Maryland Biotechnology Institute, Rockville, Maryland 20850, USA
(RECEIVED January 30, 2007; FINAL REVISION March 23, 2007; ACCEPTED March 30, 2007)
Protein G-related albumin-binding (GA) modules occur on the surface of numerous Gram-positive bacterial pathogens and their presence may promote bacterial growth and virulence in mammalian hosts. We recently used phage display selection to evolve a GA domain, PSD-1 (phage selected domain-1), which tightly bound phylogenetically diverse albumins. With respect to PSD-1s broad albumin binding specificity, it remained unclear how the evolved binding epitope compared to those of naturally occurring GA domains and whether PSD-1s binding mode was the same for different albumins. We investigate these questions here using chemical shift perturbation measurements of PSD-1 with rabbit serum albumin (RSA) and human serum albumin (HSA) and put the results in the context of previous work on structure and dynamics of GA domains. Combined, these data provide insights into the requirements for broad binding specificity in GA-albumin interactions. Moreover, we note that using the phage-optimized PSD-1 protein significantly diminishes the effects of exchange broadening at the binding interface between GA modules and albumin, presumably through stabilization of a ligand-bound conformation. The employment of artificially evolved domains may be generally useful in NMR structural studies of other proteinprotein complexes.
Keywords: albumin; protein G; hostpathogen interactions; NMR
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