Many properties of Aβ such as toxicity, aggregation and ROS formation are modulated by Cu2+. Previously, the coordination configuration and interaction of Cu2+ with the Aβ N-terminus has been extensively studied. However, the effect of Aβ C-terminal residues on related properties is still unclear. In the present study, several C-terminus-truncated Aβ peptides, including Aβ1-40, Aβ1-35, Aβ1-29, Aβ1-24 and Aβ1-16, were synthesized to characterize the effect of Aβ C-terminal residues on Cu2+ binding affinity, structure, aggregation ability and ROS formation. Results show that the Aβ C-terminal residues have effect on Cu2+ binding affinity, aggregation ability and inhibitory ability of ROS formation. Compared to the key residues responsible for Aβ aggregation and structure in the absence of Cu2+, it is more likely that residues 36–40, rather than residues 17–21 and 30–35, play a key role on the related properties of Aβ in the presence of Cu2+.

Serine proteases are among the most studied enzymes for their role as model enzymes for studying the enzyme catalytic mechanism and medical interest in their inhibition. We have applied NMR methods to determine the structure, dynamics, and catalytic mechanism of a serine protease, E. coli thioesterase/protease I (TEP-I). In this article we review the results of our efforts. We showed that TEP-I is an a /b /a -15 N NOE data revealed that TEP-I is a rigid protein with a flexible catalytic binding pocket. Slow motion involving segments around the catalytic site was detected. The formation of Michaelis complex (MC) between TEP-I and a transition state analogue, diethyl p-nitrophenyl phosphate (DENP), and its subsequent conversion to the tetrahedral complex (TC) follow a two-step process, a fast formation of MC followed by a slow conversion to TC. In both steps residues perturbed were confined mainly to four conserved segments comprising the active site. Comparable magnitudes of chemical shift perturbations were detected in both steps. From the large chemical shift perturbation upon conversion from MC to TC we proposed that the amide protons of Ser 10 and Gly 44 serve as the oxyanion-hole proton donors to stabilize the tetrahedral adduct. The pattern of residues perturbed in both steps suggests a sequential, stepwise structural change upon binding of DENP.