Amino Acid Binding to Luteinizing Hormone

Abstract

These studies demonstrate that there are significant quantities of certain amino acids bound to LH and also to its 2 chains which have been separated by countercurrent distribution. The same amino acids are present in all these preparations and they occur in approximately the same relative quantities. The amino acids were separated from LH by guanidine hydrochloride denaturation followed by Sephadex chromatography, by cellulose acetate electrophoresis, by acidifying to pH 2.2, and by oxidative sulfitolysis followed by chain separation on Sephadex. They were not separated by Sephadex chromatography in the absence of guanidine hydrochloride nor by extensive dialysis. When an LH preparation containing no free amino acids was incubated with a standard amino acid solution, serine, threonine, aspartic acid, glycine and alanine became bound to LH in approximately the same molar quantities as found in several LH preparations. The significance of these findings with respect to the interpretation of N-terminal and C-terminal determinations on LH is discussed. (Endocrinology83: 1293, 1968)