. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 200 150 100 50 AA residues from 3' ORF terminus TAA Figure 1. Secondary structure characterization for the last 195 amino acids of a putative a-Na+,K*-ATPase cDNA cloned from Stront>vloct'ii- trotus purpuratus. The Kyte-Doolittle hydropathy score suggests the pres- ence of four transmembrane domains, which match the structure of other a-Na+,K+-ATPase subumts (Blanco and Mercer. 1998). transcripts were barely detectable under the conditions we used for Northern blots of total RNA. The rapid increase in a-Na + ,K^-ATPase mR
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 200 150 100 50 AA residues from 3' ORF terminus TAA Figure 1. Secondary structure characterization for the last 195 amino acids of a putative a-Na+,K*-ATPase cDNA cloned from Stront>vloct'ii- trotus purpuratus. The Kyte-Doolittle hydropathy score suggests the pres- ence of four transmembrane domains, which match the structure of other a-Na+,K+-ATPase subumts (Blanco and Mercer. 1998). transcripts were barely detectable under the conditions we used for Northern blots of total RNA. The rapid increase in a-Na + ,K^-ATPase mRNA tran- scripts during gastrulation in 5. purpuratus was paralleled by a concomitant increase in the total activity of the sodium pump (Fig. 4). Activity levels were very low during early development in S. purpuratus and then increased after 20 h to a maximum level at the pluteus larval stage (Leong and Manahan. 1997). The rapid increase in activity between 20 and 40 h of development (Fig. 4) can be described by the exponential function (fl\) = (1 + e|lv x""4571)-': r = ; maximum activity of jumol P, h"' mg~' pro- tein]. The present study resolves the increase in enzyme. f(x)= ('0128x> r2 = I - ' - 1 - ' - 1 20 40 60 Developmental time (hours) 80 Figure 3. Relative transcript levels of the a-Na*,K*-ATPase cDNA during development in Strongylocentrotus purpuratus (quantified from Fig. 2). mRNA levels are presented relative to the maximal expression obtained at 36 h postfertilization. The rapid decline in mRNA abundance after 3f> h his a first-order exponential decay function (r = ; regression line plotted with shaded symbols). activity at a finer time scale (cf. Leong and Manahan. 1997) and reveals the close coordination between a-subunit gene transcription and the assembly of functional sodium pumps in sea urchin embryos between fertilization and gastrula- tion. Discussion It has long been a general goal of physiological ec
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