Abstract
The carbonic anhydrase nacrein participates in the formation of the nacreous or prismatic layer of Pinctada fucata. We isolated a genomic clone containing the nacrein gene and cloned the 5′-flanking region. Within the 1336 bp 5′ flanking region, we identified putative cis-acting elements, including the TATA box (TATAAAA) at −82 bp, and AP1 (−819 bp) and Oct-1 (−1244 bp) binding sites. In addition to the mantle, the nacrein gene is also expressed in the adductor muscle, liver, and foot. These results showed that nacrein not only takes part in the formation of the hard tissue but also might be involved in acid–base balance, ion transport, and maintenance of ionic concentration. In vitro transcription experiments showed that the addition of human c-jun activates transcription from the nacrein promoter. This is the first report of a promoter from a gene that controls the formation of the hard tissue of mollusk shells.
Highlights
Carbonic anhydrases (CA)(EC 4.2.1.1) are zinc-containing enzymes that catalyze the hydration of carbon dioxide and the dehydration of bicarbonate: CO2 þ H2O, HCOÀ3 þ Hþ CAs are widely distributed in all living things, from eukaryotes to prokaryotes, and play an important role in acid–base balance, ion transport, and maintenance of Biochem Genet (2012) 50:673–683 ionic concentration (Cameron 1979; Forster et al 1986; Henry 1984, 1996)
Nacrein was the first carbonic anhydrase to be discovered in the nacreous layer of Pinctada fucata (Miyamoto et al 1996)
N66 is a homolog of nacrein of Pinctada maxima, and in vitro experiments have shown that N66 strongly inhibits the crystallization of CaCO3 in the free state (Kono et al 2000)
Summary
Carbonic anhydrases (CA)(EC 4.2.1.1) are zinc-containing enzymes that catalyze the hydration of carbon dioxide and the dehydration of bicarbonate: CO2 þ H2O , HCOÀ3 þ Hþ CAs are widely distributed in all living things, from eukaryotes to prokaryotes, and play an important role in acid–base balance, ion transport, and maintenance of Biochem Genet (2012) 50:673–683 ionic concentration (Cameron 1979; Forster et al 1986; Henry 1984, 1996). There are at least five distinct CA gene families: a, b, c, d, and e (So et al 2004). Previously reported CAs are composed of a single gene, the so-called a-carbonic anhydrase (Hewett-Emmett and Tashian 1996). Five families (CAI, CAII, CAIII, CAVII, and CAXIII) are cytosolic; others are membrane-bound (CAIV, CAIX, CAXII, CAXV, and CAXIV), mitochondrial (CAVA and CAVB), or secreted (CAVI). The three isoforms that lack CA activity are known as CA-related proteins (CAVIII, CAX, and CAXI). These CAs show tissue-specific distribution (Tashian 1989; Pastorekova et al 2004)
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