It is shown here that the N-terminal domain of MDM2, which is not thought t
o bind calcium ions, otherwise bears a striking resemblance to a cluster of
four EF-hand modules like those found in the calmodulin family. There are
similarities in module arrangement, supersecondary structure and the main-c
hain to main-chain hydrogen-bonding pattern, especially in the vicinity of
the short antiparallel beta-sheet, the two strands of which lie between the
two E and F helices of tandem modules. Some conserved amino acid residues
are identified that are associated with short side-chain to main-chain hydr
ogen-bonded motifs. Also, both types of domain bind a short, functionally i
mportant hydrophobic alpha-helix from another protein in a cavity between t
he two pairs of EF-hand, or EF-hand-like, modules. (C) 1999 Academic Press.