MF7000222 SurE H234A mutant (Salmonella typhimurium) 4g9o X-ray 2.12 Homodimer Salmonella typhimurium 23409101 Mathiharan YK, Pappachan A, Savithri HS, Murthy MR PLoS ONE 2013 2 8 e55978 Domain swapping is an interesting feature of some oligomeric proteins in which each protomer of the oligomer provides an identical surface for exclusive interaction with a segment or domain belonging to another protomer. Here we report results of mutagenesis experiments on the structure of C-terminal helix swapped dimer of a stationary phase survival protein from Salmonella typhimurium (StSurE). Wild type StSurE is a dimer in which a large helical segment at the C-terminus and a tetramerization loop comprising two β strands are swapped between the protomers. Key residues in StSurE that might promote C-terminal helix swapping were identified by sequence and structural comparisons. Three mutants in which the helix swapping is likely to be avoided were constructed and expressed in E. coli. Three-dimensional X-ray crystal structures of the mutants H234A and D230A/H234A could be determined at 2.1 Å and 2.35 Å resolutions, respectively. Contrary to expectations, helix swapping was mostly retained in both the mutants. The loss of the crucial D230 OD2- H234 NE2 hydrogen bond (2.89 Å in the wild type structure) in the hinge region was compensated by new inter and intra-chain interactions. However, the two fold molecular symmetry was lost and there were large conformational changes throughout the polypeptide. In spite of these changes, the dimeric structure and an approximate tetrameric organization were retained, probably due to the interactions involving the tetramerization loop. Mutants were mostly functionally inactive, highlighting the importance of precise inter-subunit interactions for the symmetry and function of StSurE. GO:0008254 3'-nucleotidase activity GO:0008253 5'-nucleotidase activity GO:0004309 exopolyphosphatase activity GO:0046872 metal ion binding GO:0000166 nucleotide binding GO:0106411 XMP 5'-nucleosidase activity GO:0005737 cytoplasm 2 1 Homooligomeric enzymes Homodimeric enzymes All chains according to the most probable oligomerization state stored in PDBe were considered. A 5'/3'-nucleotidase SurE Salmonella typhimurium P66881 1 252 99% MRILLSNDDGVHAPGIQTLAKALREFADVQVVAPDRNRSGASNSLTLESSLRTFTFDNGDIAVQMGTPTDCVYLGVNALMRPRPDIVVSGINAGPNLGDDVIYSGTVAAAMEGRHLGFPALAVSLNGYQHYDTAAAVTCALLRGLSREPLRTGRILNVNVPDLPLAQVKGIRVTRCGSRHPADKVIPQEDPRGNTLYWIGPPGDKYDAGPDTDFAAVDEGYVSVTPLHVDLTAHSAHDVVSDWLDSVGVGTQW 253 secondary structure helix 27 38 secondary structure helix 81 92 secondary structure helix 111 115 secondary structure helix 118 127 secondary structure helix 144 162 secondary structure helix 178 182 secondary structure helix 193 197 secondary structure helix 226 233 secondary structure helix 247 259 secondary structure strand 16 20 secondary structure strand 42 48 secondary structure strand 65 69 secondary structure strand 75 77 secondary structure strand 100 107 secondary structure strand 134 140 secondary structure strand 169 175 secondary structure strand 184 187 secondary structure strand 200 203 secondary structure strand 209 212 secondary structure strand 235 244 pfam PF01975 Survival protein SurE 3 180 B 5'/3'-nucleotidase SurE Salmonella typhimurium P66881 1 253 100% MRILLSNDDGVHAPGIQTLAKALREFADVQVVAPDRNRSGASNSLTLESSLRTFTFDNGDIAVQMGTPTDCVYLGVNALMRPRPDIVVSGINAGPNLGDDVIYSGTVAAAMEGRHLGFPALAVSLNGYQHYDTAAAVTCALLRGLSREPLRTGRILNVNVPDLPLAQVKGIRVTRCGSRHPADKVIPQEDPRGNTLYWIGPPGDKYDAGPDTDFAAVDEGYVSVTPLHVDLTAHSAHDVVSDWLDSVGVGTQW 253 secondary structure helix 27 38 secondary structure helix 81 92 secondary structure helix 111 117 secondary structure helix 118 131 secondary structure helix 144 162 secondary structure helix 178 182 secondary structure helix 226 233 secondary structure helix 250 262 secondary structure strand 16 20 secondary structure strand 42 48 secondary structure strand 64 69 secondary structure strand 75 77 secondary structure strand 100 107 secondary structure strand 134 140 secondary structure strand 169 175 secondary structure strand 184 187 secondary structure strand 198 203 secondary structure strand 209 214 secondary structure strand 235 241 secondary structure strand 244 246 pfam PF01975 Survival protein SurE 3 180 Direct evidence The full structure participates in mutual synergistic folding. Survival protein SurE Two-state thermal unfolding (PMID:23409101). Domain-swapped dimer with extensive swap region and large dimer interface. Dimeric in solution (gel filtration, DLS). A N/A B N/A MF7000821 MF7000221 MF7000222 MF7000224 MF7000227 MF7000223 MF7000225 MF7000226