Analysis of the quaternary structure of the MutL C-terminal domain.
The dimeric DNA mismatch repair protein MutL has a key function in communicating mismatch recognition by MutS to downstream repair processes. Dimerization of MutL is mediated by the C-terminal domain, while activity of the protein is modulated by the ATP-dependent dimerization of the highly conserved N-terminal domain. Recently, a crystal structure analysis of the Escherichia coli MutL C-terminal dimerization domain has been reported and a model for the biological dimer was proposed. In this model, dimerization is mediated by the internal (In) subdomain comprising residues 475-569. Here, we report a computational analysis of all protein interfaces observed in the crystal structure and suggest that the biological dimer interface is formed by a hydrophobic surface patch of the external (Ex) subdomain (residues 432-474 and 570-615). Moreover, sequence analysis revealed that this surface patch is conserved among the MutL proteins. To test this hypothesis, single and double-cysteine variants of MutL were generated and tested for their ability to be cross-linked with chemical cross-linkers of various size. Finally, deletion of the C-terminal residues 605-615 abolished homodimerization. The biochemical data are fully compatible with a revised model for the biological dimer, which has important implications for understanding the heterodimerization of eukaryotic MutL homologues, modeling the MutL holoenzyme and predicting protein-protein interaction sites.
Kosinski
Jan
J
Institut für Biochemie FB 08, Justus-Liebig Universität, Giessen D-35392, Germany.
Steindorf
Ina
I
Bujnicki
Janusz M
JM
Giron-Monzon
Luis
L
Friedhoff
Peter
P
D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics; D000595:Amino Acid Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000737:chemistry; D045643:DNA Repair Enzymes / Q000737:chemistry / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics; D019281:Dimerization; D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000070956:MutL Proteins; D015202:Protein Engineering; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D013816:Thermodynamics
D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; C074770:MutL protein, E coli; D011994:Recombinant Proteins; D004706:Endodeoxyribonucleases; C059682:methyl-directed mismatch repair protein, E coli; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins; D045643:DNA Repair Enzymes; D003545:Cysteine