Representation of Lck(64–120) structure. A: Overlay of 25 structures of Lck(64–120). Structures were fitted to backbone atoms of residues 64 to 120. The backbone is colored in black, side chains are colored in light gray. B: The structure of Lck(64–120) is shown as ribbon diagram. C: Superposition of the crystal structure (black)  and the solution structure (gray) with the lowest energy of the Lck SH3 domain.