Primary structure of a C-hordein gene from barley

Abstract

The nucleotide sequence of a 2065 base pair HindIII fragment, containing a gene (λhor1-14) belonging to the Hor1 locus in barley, has been determined. The fragment consists of 1044 bp of coding region interrupted by an amber codon at base 481, a 5′ non-coding region of 428 bp and a 3′ non-coding region with 593 bp. The deduced amino acid sequence of the mature protein (327 amino acids) is characterized by an octapeptide motif PQQPFPQQ which is repeated throughout the peptide chain between a unique 12 amino acid long NH₂-terminal and an equally unique 10 amino acid long COOH-terminal end. The proline+glutamine content is 62% and the next three most abundant amino acids are leucine (9%), phenylalanine (8%) and isoleucine (3%). In the 5′ non-coding region there is a TATA box at −98 bp from the start methionine. The 3′ non-coding region has a polyadenylation signal 76 bp downstream from the TAA stop codon. The deduced amino acid sequences of the NH₂- and COOH-terminals of λhor1-14 are very similar but not identical to those known from the Edman degradation and carboxypeptidase Y analysis of C-hordein polypeptides. The 3′ coding and non-coding region of λhor1-14 is closely similar but different in detail to the known C-hordein cDNA clones. One polyadenylation signal is found in λhor1-14 whereas two are present in each of the three known C-hordein cDNAs. These differences and the amber codon interrupting the open reading frame indicate that this gene is silent.