Molecular structure of human seminal coagulum: the role of disulfide bonds.

Using sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis in the presence of 100 mM 2-mercaptoethanol, freshly ejaculated human semen showed two major protein bands of 72 and 55 kd. During liquefaction these two protein bands were degraded to low molecular weight proteins of 10-15 kd. In the absence of 2-mercaptoethanol, larger proteins such as those of 243, 221 and 195 kd were obtained which could be converted to 72 and 55 kd proteins by the action of the sulfhydryl reducing agent. Liquefaction was enhanced in the presence of 2-mercaptoethanol. These results indicated that one of the factors involved in the formation of human seminal coagulum is disulfide linkage between proteins of 72 and 55 kd.