TY - JOUR
T1 - Plasmodium falciparum SSB tetramer wraps single-stranded DNA with similar topology but opposite polarity to E. Coli SSB
AU - Antony, Edwin
AU - Weiland, Elizabeth A.
AU - Korolev, Sergey
AU - Lohman, Timothy M.
N1 - Funding Information:
The P. falciparum genomic DNA was a kind gift from Dr. Daniel Goldberg (Washington University School of Medicine). We thank Dr. Alex Kozlov and Dr. Binh Nguyen for significant technical advice and Mr. Thang Ho for synthesis and purification of the oligodeoxynucleotides. This work was supported in part by grants from the National Institutes of Health to T.M.L. ( GM30498 and GM45948 ) and S.K. ( GM073837 ).
PY - 2012/7/20
Y1 - 2012/7/20
N2 - Single-stranded DNA binding (SSB) proteins play central roles in genome maintenance in all organisms. Plasmodium falciparum, the causative agent of malaria, encodes an SSB protein that localizes to the apicoplast and likely functions in the replication and maintenance of its genome. P. falciparum SSB (Pf-SSB) shares a high degree of sequence homology with bacterial SSB proteins but differs in the composition of its C-terminus, which interacts with more than a dozen other proteins in Escherichia coli SSB (Ec-SSB). Using sedimentation methods, we show that Pf-SSB forms a stable homo-tetramer alone and when bound to single-stranded DNA (ssDNA). We also present a crystal structure at 2.1 Å resolution of the Pf-SSB tetramer bound to two (dT)35 molecules. The Pf-SSB tetramer is structurally similar to the Ec-SSB tetramer, and ssDNA wraps completely around the tetramer with a baseball seam topology that is similar to Ec-SSB in its 65 binding mode. However, the polarity of the ssDNA wrapping around Pf-SSB is opposite to that observed for Ec-SSB. The interactions between the bases in the DNA and the amino acid side chains also differ from those observed in the Ec-SSB-DNA structure, suggesting that other differences may exist in the DNA binding properties of these structurally similar proteins.
AB - Single-stranded DNA binding (SSB) proteins play central roles in genome maintenance in all organisms. Plasmodium falciparum, the causative agent of malaria, encodes an SSB protein that localizes to the apicoplast and likely functions in the replication and maintenance of its genome. P. falciparum SSB (Pf-SSB) shares a high degree of sequence homology with bacterial SSB proteins but differs in the composition of its C-terminus, which interacts with more than a dozen other proteins in Escherichia coli SSB (Ec-SSB). Using sedimentation methods, we show that Pf-SSB forms a stable homo-tetramer alone and when bound to single-stranded DNA (ssDNA). We also present a crystal structure at 2.1 Å resolution of the Pf-SSB tetramer bound to two (dT)35 molecules. The Pf-SSB tetramer is structurally similar to the Ec-SSB tetramer, and ssDNA wraps completely around the tetramer with a baseball seam topology that is similar to Ec-SSB in its 65 binding mode. However, the polarity of the ssDNA wrapping around Pf-SSB is opposite to that observed for Ec-SSB. The interactions between the bases in the DNA and the amino acid side chains also differ from those observed in the Ec-SSB-DNA structure, suggesting that other differences may exist in the DNA binding properties of these structurally similar proteins.
KW - DNA repair
KW - Plasmodium and malaria
KW - recombination
KW - replication
KW - structure
UR - http://www.scopus.com/inward/record.url?scp=84862208973&partnerID=8YFLogxK
U2 - 10.1016/j.jmb.2012.04.021
DO - 10.1016/j.jmb.2012.04.021
M3 - Article
C2 - 22543099
AN - SCOPUS:84862208973
SN - 0022-2836
VL - 420
SP - 269
EP - 283
JO - Journal of Molecular Biology
JF - Journal of Molecular Biology
IS - 4-5
ER -