The calcium-binding protein S100A3 is an unusual member of the S100 family, characterized by its very high content of Cys. In order to study the biochemical, cation-binding, and conformational properties, we produced and purified the recombinant human protein in Escherichia coli. . Since no Zn 2؉ -binding motif of known structure was identified in the primary sequence of S100A3, the results are suggestive for a novel Zn 2؉ -binding motif.

α and β parvalbumins are Ca2+‐binding proteins of the EF‐hand type. We determined the protein sequence of human brain α parvalbumin by mass spectrometry and cloned human β parvalbumin (or oncomodulin) from genomic DNA and preterm placental cDNA. β parvalbumin differs in 54 positions from α parvalbumin and lacks the C‐terminal amino acid 109. From MS analyses of α and β parvalbumins we conclude that parvalbumins generally lack posttranslational modifications. α and β parvalbumins were differently expressed in human tissues when analyzed by immunoblotting and polymerase‐chain‐reaction techniques. Whereas α parvalbumin was found in a number of adult human tissues, β parvalbumin was restricted to preterm placenta. The pattern of α parvalbumin expression also differs in man compared to other vertebrates. For example, in rat, α parvalbumin was found in extrafusal and intrafusal skeletal‐muscle fibres whereas, in man, α parvalbumin was restricted to the muscle spindles. Different functions for α and β parvalbumins are discussed.

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