Calcium-binding proteins, basement membranes

Normally a preponderance of negative charges would be expected due to the fact that the sarcolemma membrane consists of a superficially located "basement membrane" and a plasma membrane which contains an abundance of negatively charged free or protein bound mucopolysaccharide material with specific affinity for calcium. Negatively charged phosphorylated proteins superficially located in the sarcolemma membrane also act as binding sites for calcium. 

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