Details

Autor(en) / Beteiligte

• Aishima, Jun

Titel

Structural and biochemical studies of the MATalpha2 homeodomain protein from yeast

Ort / Verlag

ProQuest Dissertations & Theses

Erscheinungsjahr

2002

Quelle

ProQuest Dissertations & Theses A&I

Beschreibungen/Notizen

• The MATα2 protein is involved in mating type determination in the yeast, Saccharomyces cerevisiae. MATα2 binds sequences upstream of a-specific and haploid-specific gene promoters using a homeodomain, which recognizes specific sequences of DNA. To better understand the way that homeodomains recognize DNA, I have solved the 2.1 Å crystal structure of the MATα2 homeodomain bound to DNA. Surprisingly, I found four MATα2 homeodomains (abbreviated α2) bound to DNA, instead of the expected two. The extra homeodomain proteins may have bound to DNA in this structure due to their stronger binding affinity, as well as the crystal packing changes resulting from the use of a shorter α2 fragment in this crystal structure. The DNA in the crystal structure contains the first known case of a Hoogsteen base pair in a crystal structure that contains straight B-DNA. This Hoogsteen base pair appears to be stabilized by favorable base stacking and hydrogen bonds within the DNA, as well as by an interaction with an α2 homeodomain. The Hoogsteen base pair, however, does not form in the absence of bound α2 proteins, as shown by NMR experiments. I verified that Hoogsteen base pairs were not observed in other protein/DNA structures containing straight B-DNA. Molecular dynamics simulations show that a bound homeodomain stabilizes the Hoogsteen base pair.