Protein hydrolysis electrostatic effects

To test the dominance of electrostatic effects in the mineralization model, a mutant of CCMV was constructed (subE) in which all the basic residues on the N-terminus of the coat protein were substituted for glutamic acid (E), thus dramatically altering the electrostatic character of the interior of the assembled protein cage." This mutant was able to catalyze the oxidative hydrolysis of Fe(II) to form an iron oxide nanoparticle encapsulated within the protein cage of the modified virus. High-rcsolution spectral imaging allowed the elemental composition of a protein-mineral composite material to be resolved (1 nm spatial resolution, Fig. 3). This clearly showed that the mineral nanoparticle was completely encapsulated within the protein cage structure. This mutant is able to bind Fe(lT), facilitate its autoxidation... 

As mentioned above, various proteins are able to form electrostatic complexes with HA. We thus decided to investi te the effect of the presence of a protein with no catalytic activity towards HA on the kinetics of the HA hydrolysis catalyzed by BT-HAase. For that purpose, we chose to first use BSA. Indeed, BSA is known as to be able to form electrostatic corrrplexes with HA. In addition, BSA is a rrtajor protein of synovial fluid (Scott et al., 2000), a flrrid which is also rich in HA (see Irrtroduction section). Figure 6 shows BSA-deperrdence crrrves (that is to say, irritial hydrolysis rate plotted as a function of the BSA concentration) obtained for variorrs HA concentrations, at pH 4 and at low ionic strength (5 mmol 1 ). We can observe (Figure 6) that (i) the initial rate of HA hydrolysis catalyzed by BT-HAase strongly depertded on the BSA concentration and (ii) the BSA-deperrdence ciuves had all the same shape whatever the HA concerrtration (Lenormand et al., 2009). 

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