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Structure of the month - February 2007

Fischer_February07_fig1 - enlarged view

Figure 1. Structure of C. reinhardtii MCP monomer (A) and tetramer (B). Residues G70 and I76 that border a stretch of delocalized residues are highlighted.

Fischer_February07_fig2 - enlarged view

Figure 2. Substrate-binding site of MCP. (A) Transparent surface view with residues that are highly flexible highlighted in red and residues that were subjected to structure-based mutagenesis highlighted in blue. (B) Electrostatic surface potential. (C) Sequence alignment of MCP residues 38-75 with homologous proteins from Crocosphaera watsonii (EAM49636), Trichodesmium erythraeum (EAO26031), Methanopyrus kandleri (NP_614673), Aquifex aeolicus (NP_213091), Thermotoga maritima (NP_228861), Archaeoglobus fulgidus (AAB90115), Rhodobacter sphaeroides (EAP67917), Synechococcus sp. (YP_381580), Dictyostelium discoideum (EAL66951), Oryza sativa (BAD46468), and Arabidopsis thaliana (AAM64859). The alignment was generated with ClustalW and the first residue of each sequence line is shown. (D) Stability of Moco bound to MCP wild type and mutant variants M50A and P69A at 4°C (E) and 22°C. 1000 pmol wild type and mutant protein were incubated the indicated times and Moco content was determined by HPLC analysis.

Fischer_February07_tab1 - enlarged view

Table 1. X-ray data collection and refinement statistics.
Rsym =ΣhklΣi|Ii - (I)| ΣhklΣi(I) where Ii is the i-th measurement and (I) is the weighted mean of all measurements of I. (I)/(σI) indicates the average of the intensity divided by its average standard deviation. Rcryst =Σ||Fo| - |Fc|| / Σ|Fo| where Fo and Fc are the observed and calculated structure factor amplitudes. Rfree same as Rcryst for 5% of the data randomly omitted from the refinement. Ramachandran statistics indicate the fraction of residues in the most favored, additionally allowed, generously allowed, and disallowed regions of the Ramachandran diagram, as defined by PROCHECK.