Parvalbumin alpha is a 12 kDa member of the parvalbumin family of Ca2+-binding proteins. In human, it is expressed in intrafusal muscle fibers, plus GABAergic interneurons and cerebellar Purkinje and basket cells. It presumably acts as a Ca2+ buffer that shortens the duration of fiber contraction. Human Parvalbumin is 110 amino acids (aa) in length. It contains two EF-hand domains (aa 39 - 74 and 78 - 110) that bind calcium. There are three potential isoform variants. One shows an alternate start site at Met33, a second shows a six aa substitution for the C-terminal nine amino acids and a third shows a deletion of Gly99 - Val100. Human Parvalbumin alpha is 51% aa identical to human Parvalbumin beta and is 87% plus 92% aa identical to mouse and rat Parvalbumin, respectively.