The accessory fibers of the sperm tail: III. High-sulfur and low-sulfur components in mammals and cephalopods

Abstract

Purified mammalian accessory fibers consist of two groups of disulfide-cross-linked polypeptide chains: The high molecular weight chains (42 000–72 000 daltons) are rich in aspartic acid, glutamic acid, and leucine; the low molecular weight chains (28 000–31 000 daltons) are rich in cysteine and proline. The infrared spectrum of whole fibers is similar to that of keratin. Protofibril-like structures, 2 nm thick, are detected in native fibers and become more evident after proteolysis or “renaturation” from guanidine-HC1 solutions. The cross-striation of accessory fibers originates from the lateral packing of protofibril-like units. Cephalopod accessory fibers are also resolved into two groups of disulfide-cross-linked chains: as in mammalian fibers, the high molecular weight chains (about 90 000 daltons in both Eledone moschata and E. cirrhosa) contain large amounts of aspartic acid, glutamic acid, and leucine; the low molecular weight group (about 50 000 and 30 000 daltons in E. moschata, 36 000 daltons in E. cirrhosa) contains large amounts of cysteine, proline, and histidine. The occurrence of low-sulfur and high-sulfur polypeptides, the zinc-binding properties (6), and the analogous localization in wave-generating flagella prompt the authors to distinguish the keratin-like proteins of sperm accessory fibers of mammals and cephalopods with the new name of parergins.