Role of tyrosine M210 in the initial charge separation of reaction centers of Rhodobacter sphaeroides

Abstract
Femtosecond spectroscopy was used in combination with site-directed mutagenesis to study the influence of tyrosine M210 (YM210) on the primary electron transfer in the reaction center of Rhodobacter sphaeroides. The exchange of YM210 to phenylalanine caused the time constant of primary electron transfer to increase from 3.5 .+-. 0.4 ps to 16 .+-. 6 ps while the exchange to leucine increased the time constant even more to 22 .+-. 8 ps. The results suggest that tyrosine M210 is important for the fast rate of the primary electron transfer.