span>threonine <span  title="" class="an ">&ensp;</span>Thr <span  title="" class="an ">&ensp;</span>Low <span  title="" class="an ">&ensp;</span>concentrations <span  title="" class="an ">&ensp;</span>of <span  title="" class="an ">&ensp;</span><span  title="CAP" class="an CAP">SP</span><span  title="" class="an ">&ensp;</span>x <span  title="" class="an ">&ensp;</span>M <span  title="" class="an ">&ensp;</span>caused <span  title="" class="an ">&ensp;</span>a <span  title="" class="an ">&ensp;</span>selec