HUMAN ALPHA-PARVALBUMINS AND BETA-PARVALBUMINS - STRUCTURE AND TISSUE-SPECIFIC EXPRESSION

Alpha and beta parvalbumins are Ca2+-binding proteins of the EF-hand t ype. We determined the protein sequence of human brain alpha parvalbum in by mass spectrometry and cloned human beta parvalbumin (or oncomodu lin) from genomic DNA and preterm placental cDNA. Beta parvalbumin dif fers in 54 positions from alpha parvalbumin and lacks the C-terminal a mino acid 109. From MS analyses of alpha and beta parvalbumins we conc lude that parvalbumins generally lack posttranslational modifications. Alpha and beta parvalbumins were differently expressed in human tissu es when analyzed by immunoblotting and polymerase-chain-reaction techn iques. Whereas alpha parvalbumin was found in a number of adult human tissues, beta parvalbumin was restricted to preterm placenta. The patt ern of alpha parvalbumin expression also differs in man compared to ot her vertebrates. For example, in rat, alpha parvalbumin was found in e xtrafusal and intrafusal skeletal-muscle fibres whereas, in man, alpha parvalbumin was restricted to the muscle spindles. Different function s for alpha and beta parvalbumins are discussed.