| Abstract
| - Members of the cysteine and glycine-rich protein (CRP)family (CRP1, CRP2, and CRP3)contain two zinc-binding LIM domains, LIM1 and LIM2, and are implicatedin diverse cellular processeslinked to differentiation, growth control and pathogenesis. Thesolution structure of an 81-amino acidrecombinant peptide encompassing the amino-terminal LIM1 domain ofquail CRP2 has been determinedby 2D and 3D homo- and heteronuclear NMR spectroscopy. The LIM1domain consists of two zincbinding sites of the CCHC and the CCCC type, respectively, which bothcontain two orthogonally arrangedantiparallel β-sheets and which are packed together by a hydrophobiccore composed of residues fromthe zinc finger loop regions. The CCCC zinc finger is followed bya short α-helical stretch. The structuralanalysis revealed that the global fold of LIM1 closely resembles therecently determined solution structuresof the carboxyl-terminal LIM2 domains of quail CRP2 and chicken CRP1,and that LIM1 and LIM2 areindependently folded structural and presumably functional domains ofCRP proteins. To explore thedynamical properties of CRP proteins, we have used 15Nrelaxation values (T1,T2, and nuclear Overhausereffect (NOE) to describe the dynamical behavior of a LIM domain. Amodel-free analysis revealed localvariations in mobility along the backbone of the quail CRP2 LIM1 motif.Slow motions are evident inturn regions located between the various antiparallel β-sheets orbetween their strands. By use of anextended motional model, fast backbone motions were detected forbackbone amide NH groups ofhydrophobic residues located in the core region of the LIM1 domain.These findings point to a flexiblehydrophobic core in the LIM1 domain allowing residual relative mobilityof the two zinc fingers, whichmight be important to optimize the LIM1 interface for interaction withits physiological target molecule(s)and to compensate enthalpically for the entropy loss uponbinding.
|
