The solution structure of cytochrome c(6) from the green alga Monoraphidium braunii

The three-dimensional structure in solution of the reduced form of cytochrome c(6) from the green alga Monoraphidium braunii has been solved through NMR data. Cytochrome c(6) acts as a small mono-heme electron carrier protein between the two membrane-embedded complexes cytochrome f and photosystem I. The structure was determined using 1278 relevant interproton NOEs out of 1776 assigned NOEs with distance geometry (DG) calculations which included 36 stereospecific assignments and 20 experimentally found angle constraints. The family of structures obtained from the DG calculations was subjected to energy minimization and molecular dynamics simulation using previously defined force field parameters for the heme and its ligands. In all stages of the calculations, the solution structure is well defined and similar to the now available X-ray structure.