2-DIMENSIONAL ARRANGEMENT OF A FUNCTIONAL PROTEIN BY CYSTEINE-GOLD INTERACTION - ENZYME-ACTIVITY AND CHARACTERIZATION OF A PROTEIN MONOLAYER ON A GOLD SUBSTRATE

We have characterized the functional protein, myosin subfragment 1 (S1 ), attached to a gold substrate by the sulfhydryl groups of cysteine i n proteins. The amino groups of the regulatory light chain (RLC) isola ted from myosin were labeled with a radioisotope (I-125), and the labe led RLC was incorporated into S1 from which the RLC had been removed. The radiation from I-125 showed that S1 molecules had attached to the gold and, through the interference effect of the monochromatic radiati on from I-125, provided information about the position of labeled RLC sites in the S1 monolayer. The interference fringes showed that the RL C was located close to the gold surface and that all of the adsorbed S 1 molecules had the same orientation. We confirmed that the motor func tion of S1 on the gold surface is maintained by observing sliding move ment at low ionic strength and by observing the detachment at high ion ic strength of fluorescent actin filaments in the presence of ATP. We also found that the adsorbed S1 molecules were not removed from the Au surface by a reducing agent. Thus the Au-S bond is more stable than t he S-S bond.