@Article{IPB-1296, author = {Morgan, K.E. and Zarembinski, T.I. and Theologis, A. and Abel, S.}, title = {{Biochemical characterization of recombinant polypeptides corresponding to the predicted ßαα-fold in Aux/IAA proteins}}, year = {1999}, pages = {283-287}, journal = {FEBS Letters}, url = {http://www.febsletters.org/article/S0014-5793%2899%2900819-4/abstract}, volume = {454}, abstract = { The plant hormone indoleacetic acid (IAA or auxin) transcriptionally activates a select set of early genes. The Auxl IAA class of early auxin-responsive genes encodes a large family of short-lived, nuclear proteins. Aux/IAA polypeptides homo-and heterodimerize, and interact with auxin-response transcription factors (ARFs) via C-terminal regions conserved in both protein families. This shared region contains a predicted βαα motif similar to the prokaryotic β-Ribbon DNA binding domain, which mediates both protein dimerization and DNA recognition. Here, we show by circular dichroism spectroscopy and by chemical cross-linking experiments that recombinant peptides corresponding to the predicted βαα region of three Aux/IAA proteins from Arabidopsis thaliana contain substantial α-helical secondary structure and undergo homo- and heterotypic interactions in vitro. Our results indicate a similar biochemical function of the plant βαα domain and suggest that the βαα fold plays an important role in mediating combinatorial interactions of Aux/IAA and ARF proteins to specifically regulate secondary gene expression in response to auxin.} }