Proteome analysis of light-induced proteins in Synechocystis sp PCC 6803: Identification of proteins separated by 2D-PAGE using N-terminal sequencingand MALDI-TOF MS

The cyanobacterium Synechocystis sp. PCC 6803 is an ideal model organism fo r the proteome study of light-induced gene expression because the whole gen omic sequence has been determined. The soluble proteins extracted from ligh t- and dark-cultured cells were separated by two-dimensional polyacrylamide get electrophoresis. Light-induced protein spots electroblotted on a polyv inyldiene difluoride membrane were analyzed by N-terminal Edman sequence de termination and followed by CyanoBase. The tryptie digests of some proteins were also confirmed by matrix-assisted laser desorption ionization/time-of -flight (MALDI-TOF) and MS-Fit search. Interestingly, eight proteins were r elated to photosynthesis and respiration (RbcS/L, CbbA, Gap2, AtpB, CpcB, P sbO, and PsbU). Four proteins (SodB, DnaK, GroEL2, and Tig) were involved i n cellular processes and the functions of another two proteins (rehydrin an d membrane protein) were unknown. The proteome analysis by N-terminal Edman sequencing and MALDI-TOF enabled us to characterize one-shot protein profi les expressed under different physiological conditions.