Human spermatozoa with normal structure and with different axonemal deficiencies (absence of axoneme, of arms, or of central structures) were studied by electron microscopy, SDS-polyacrylamide gel electrophoresis, and ATPase activity measurements. Normal human sperm possess a complement of high molecular weight polypeptides with an electrophoretic migration similar to that of sea urchin and other mammalian sperm dyneins. Human high molecular weight bands are numbered one to four in order of increasing of electrophoretic mobility; all of them are absent in spermatozoa that lack axoneme. The absence of doublet arms, coincides with the absence of bands 2, 3, and 4; the absence of central structures coincides with a reduction in intensity of band 2. In the latter two abnormal conditions, band 1 has an increased intensity. The data are tentatively interpreted by attributing the polypeptides forming bands 3 and 4 to the arm structure, whereas band 2 is supposed to contain a mixture of polypeptides localized in the arms and in the central structures; these abnormal sperm contain modified polypeptides which gather in band 1. Histochemical ATPase stainings indicate that this enzyme is localized mainly in the doublet arms and, to a minor extent, in the central structures.
Two unconventional sperm models (all motile) have been studied. The first one has only the outer arm on the doublets (the gall midge, Diplolaboncus); the second one, has only a well-developed inner arm (the eel, Anguilla). Both are devoid of central tubules and radial spokes. The gall midge sperm yields a single electrophoretic band migrating similarly to the sea urchin dynein band A; a major high-molecular-weight band is obtained from eel sperm which co-migrates with the sea urchin dynein band B. The present picture is consistent with the localization of dynein in the axoneme--namely, of an A-like band in the outer arm, and of the B band in the inner arm. Moreover, the D band is present only in the eel, where gamma-links are present. ATPase activity was localized histochemically and found to be associated with both inner and outer arms, as well as with the gamma-links.
Mitochondrial derivatives of insect sperm usually contain a crystalline protein that shows a 45-nm main period, made up of 20-nm subperiods, determined by the coiling of filament bundles. Filaments are 2 nm thick and have a globular appearance. The crystals contain two main polypeptides, 52,000 and 55,000 daltons. These polypeptides are closely related, contain a high percentage of proline, and are insoluble in sodium dodecyl sulfate due to disulfide cross links. We suggest for this class of protein the name crystallomitin.