The structure and evolution of the spider monkey delta-globin gene

We have isolated the delta-globin gene of the New-World spider monkey, Ateles geoffroyi, and compared its nucleotide sequence with those of other primate delta- and beta-globin genes. Among primate delta-globin genes, the rate of nonsynonymous substitutions is much less than the rate of synonymous substitutions. This suggests that primate delta- globin genes may remain under evolutionary conservation, perhaps because hemoglobin A2 has an as yet unknown physiological importance.      

Calcium-activated potassium channels expressed from cloned complementary DNAs.

Calcium-activated potassium channels were expressed in Xenopus oocytes by injection of RNA transcribed in vitro from complementary DNAs derived from the slo locus of Drosophila melanogaster. Many cDNAs were found that encode closely related proteins of about 1200 aa. The predicted sequences of these proteins differ by the substitution of blocks of amino acids at five identified positions within the putative intracellular region between residues 327 and 797. Excised inside-out membrane patches showed potassium channel openings only with micromolar calcium present at the cytoplasmic side; activity increased steeply both with depolarization and with increasing calcium concentration. The single-channel conductance was 126 pS with symmetrical potassium concentrations. The mean open time of the channels was clearly different for channels having different substituent blocks of amino acids. The results suggest that alternative splicing gives rise to a large family of functionally diverse, calcium-activated potassium channels.     

Cryopreservation, actin localization and thermotropic phase transitions in ram spermatozoa

The effects of controlled stress, i.e. cooling, upon the distribution of actin in ram spermatozoa were examined to investigate the hypothesis that cytoskeletal proteins are involved in the maintenance of sperm plasma membrane integrity. The normal distribution of actin on the spermatozoon was initially determined. A monoclonal antibody (IgM) interacted exclusively with the post-acrosomal region and the principal piece of the flagellum. By the use of a polyclonal antibody, actin was detected on the acrosome (excluding the equatorial segment), the post-acrosomal region and the whole of the flagellum. The actin was present in its non-filamentous form. Spermatozoa fixed at 39 degrees C and then treated for the immunofluorescent detection of actin with the monoclonal antibody were mostly unstained (proportion stained = 4.4% (+/- 1.6; s.e.m.); n = 8 ejaculates). Provided spermatozoa were permeabilized by greater than 0.025% Triton X-100 before immunofluorescence, actin was localized in the postacrosomal region of all sperm heads, and to a minor extent on the principal piece of the flagellum. Use of the polyclonal antibody confirmed that the post-acrosomal antigen was unmasked by detergent treatment. Slow cooling, over 2-h periods to various temperatures between 5 and 15 degrees C, also induced an increase in the proportion of cells showing post-acrosomal actin immunoreactivity. Cooling through the temperature range 15 to 10 degrees C markedly increased the proportion of immunoreactive cells (mean +/- s.e.m.; 12 +/- 4.5% at 15 degrees C; 27 +/- 4.5% at 10 degrees C; n = 4 ejaculates). Further cooling to 5 degrees C failed to elicit increased staining. Ultrastructural examination of cooled spermatozoa confirmed that a subpopulation of spermatozoa exhibited post-acrosomal actin immunoreactivity after cooling. These results are compatible with the suggestion that actin fulfills a stabilizing function in spermatozoa.     

Biochemical pathways in prokaryotes can be traced backward through evolutionary time

For the first time, a credible prokaryotic phylogenetic tree is being assembled by Woese and others using quantitative sequence analysis of oligonucleotides in the highly conservative rRNA. This provides an evolutionary scale against which the evolutionary steps that led to the arrangement and regulation of contemporary biochemical pathways can be measured. This paper presents an emerging evolutionary picture of aromatic amino acid biosynthesis within a large superfamily assemblage of prokaryotes that is sufficiently developed to illustrate a new perspective that will be applicable to many other biochemical pathways.