E31-K352, the minimal cation binding moiety of Na+,K(+)-ATPase

Upon limited tryptic fragmentation of Na+,K(+)-ATPase a 35 kDa fragment (E31-K352) was formed that bound 204Tl+ on blot. Further fragmentation led to loss of binding, pointing to the conclusion that E31-K352 is the minimal cation binding unit in Na+,K(+)-ATPase.