33kDa extrinsic protein, an important protein in oxygenic photosynthesis, was known to have no fixed configuration in solution. At 20$^{C}$ and pH 6, 33kDa extrinsic protein showed changes of free energy of -14.6 kJ/mor$^$-1/ and of standard volume of -120mL/mol, respectively, with increase of hydrostatic pressure, comparatively lower than for most proteins. NBS modification of Trp241 in 33kDa extrinsic protein dramatically changes the secondary protein structure, its affinity to photosystem II as well as photosynthetic oxygen evolution. The relationship between structural change and transport of oxygen, water and proton is deserved a further study.