Effects of lysine and glutamic acid or [corrected] Mg++ on the conformations of C3 and B, and the activation of the alternative complement pathway.

The conversion of C3 and B in the mixture of C3, B, D and Mg++ ions was inhibited in the presence of arginine and lysine, but not in the presence of glutamic acid and aspartic acid among other amino acids. Application of dialyzed plasma to a lysine-Sepharose column resulted in elution of B and a part of D in pass-through fractions, and C3 and the other part of D were retained in the column, subsequently eluted by increase in salt concentrations. C3, B and a part of D were eluted in pass-through fractions, and C3 and the other part of D were retained in the column, subsequently eluted by increase in salt concentrations. C3, B and a part of D were eluted in pass-through fractions when applied to glutamic acid-Sepharose. A highly purified D preparation appeared in the pass-through fraction of the lysine-Sepharose column, suggesting that D may form a complex in plasma. The intensity of intrinsic fluorescence of C3 decreased in the presence of arginine to the largest extent. Lysine affected the intensity less than arginine. Kd was calculated to be 0.42 mM for arginine and 0.55 mM for lysine in the interaction with C3. The intensity of intrinsic fluorescence of B decreased in the presence of aspartic acid and glutamic acid (Kd = 0.48 mM for aspartic acid and 0.24 mM for glutamic acid). Arginine or lysine affected the intensity of B less than those anionic amino acids. The presence of Mg++ ions resulted in a decrease in the fluorescence intensity of C3 and B.(ABSTRACT TRUNCATED AT 250 WORDS)