un ting ▁cone ▁sn ails ▁of ▁the ▁Amer icas ▁( Con us ▁pur pur asc ens ▁and ▁Con us ▁er mine us , ▁respectively ). ▁ ▁Con - P ▁diff ers ▁from ▁the ▁other ▁known ▁con ant ok ins ▁in ▁that ▁it ▁contains ▁a ▁long ▁dis ulf ide ▁loop ▁with ▁two ▁Gla ▁resid ues . ▁ ▁It ▁is ▁less ▁hel ical ▁( est im ated ▁ 4 4 % ▁hel ical ▁content ), ▁but ▁unlike ▁con - G , ▁it ▁does ▁not ▁require ▁calci um ▁for ▁stability ▁of ▁this ▁structure . ▁ ▁Another ▁notable ▁distinction ▁is ▁the ▁increased ▁disc rim ination ▁for ▁NR 2 B . ▁ ▁Con - E ▁is ▁very ▁similar ▁in ▁structure ▁to ▁Con - P , ▁and ▁is ▁likely ▁to ▁have ▁a ▁similar ▁function . ▁ ▁Con ant ok in - R l - A ▁ ▁Con - R l - A ▁( ), ▁derived ▁from ▁the ▁ven om ▁of ▁Con us ▁rol ani , ▁is ▁unique ▁among ▁the ▁con ant ok ins ▁in ▁having ▁two ▁distinct ▁conform ational ▁states ▁between ▁which ▁it ▁equilib ri ates . ▁ ▁Like ▁Con - P ▁and ▁Con - E , ▁its ▁hel ical ▁structure ▁( est im ated ▁at ▁ 5 0 %) ▁does ▁not ▁depend ▁on ▁the ▁presence ▁or ▁absence ▁of ▁calci um . ▁ ▁This ▁is ▁likely ▁due ▁to ▁the ▁fact ▁that ▁two ▁of ▁the ▁five ▁Gla ▁resid ues ▁present ▁in ▁con - G ▁are ▁replaced ▁in ▁con - R l - A ▁by ▁L ys . ▁Con - R