Concerted Formation of Macromolecular Suppressor–mutator Transposition Complexes

Ramesh Raina, Pennsylvania State University
Michael Schläppi, Marquette University
Balasulojini Karunanandaa, Pennsylvania State University
Adam Elhofy, Tulane University of Louisiana
Nina V. Fedoroff, Pennsylvania State University

Proceedings of the National Academy of Sciences, Vol. 95, No. 15 (July 21, 1998): 8526-8531. Permalink.

Michael Schläppi was affiliated with the Carnegie Institution of Washington at the time of publication.


Transposition of the maize Suppressor–mutator (Spm) transposon requires two element-encoded proteins, TnpA and TnpD. Although there are multiple TnpA binding sites near each element end, binding of TnpA to DNA is not cooperative, and the binding affinity is not markedly affected by the number of binding sites per DNA fragment. However, intermolecular complexes form cooperatively between DNA fragments with three or more TnpA binding sites. TnpD, itself not a sequence-specific DNA-binding protein, binds to TnpA and stabilizes the TnpA–DNA complex. The high redundancy of TnpA binding sites at both element ends and the protein–protein interactions between DNA-bound TnpA complexes and between these and TnpD imply a concerted transition of the element from a linear to a protein crosslinked transposition complex within a very narrow protein concentration range.