Normal mode analysis of mouse epidermal growth factor: characterization of the harmonic motion.

Normal mode analysis of mouse epidermal growth factor (mEGF) has been carried out at room temperature. The value of the lowest frequency is 4.1 cm-1. This mode corresponds to hinge-bending motion between the N-terminal and C-terminal domains of mEGF. This hinge-bending motion corresponds to the "mitten mode." In this motion, the N-terminal domain is almost rigid. However, the C-terminal domain is found to consist of three rigid segments. Two segments, C33-D46 and G51-R53, are observed moving in the same direction, but L47-W50 moves in the opposite direction. For this mode, the effective Young's modulus turned out to be 1.1 x 10(9) dyn.cm-2. This value is a little larger than that of the mode with the lowest frequency 4.4 cm-1 of BPTI. The difference may be related to the fraction of residues involved in beta-sheets in the molecule. Similar analyses are carried out for other low frequency modes.