Role of Trp-187 in the annexin V-membrane interaction: A molecular mechanics analysis

The minimized energy mapping of annexin V Trp-187 chi(1) x chi(2) isomeriza tion supports the existence of two preferential rotameric orientations of t he Trp side chain upon annexin V binding to membranes, in agreement with th e time-resolved fluorescence results. They correspond to the perpendicular trans (-173 degrees, 73 degrees) and g(-) (-71 degrees, 83 degrees) rotamer s and represent 59 and 28% of the population, respectively, The analysis of their local environment makes it possible to assign the trans rotamer to t he long component and the g(-) rotamer to the short component of the biexpo nential fluorescence decay, The orientation of these rotamers relative to t he protein core suggests a dual role for Trp-187, which might be involved b oth in the interaction with the phospholipid bilayer and in the formation o f the annexin V 2-D array at the surface of the membrane. (C) 1999 Academic Press.