Characterization of Polypeptides Corresponding to Clones of Maize Zein mRNAS (original) (raw)
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Solution conformational analysis of the α-zein proteins of maize. J. Biol. Chem 268:26253-26259
Journal of Biological Chemistry
Small angle x-ray scattering and viscometric analyses of the a-zeins of maize in solution indicated that the molecules were asymmetric. Structure predictions of consensus sequences for the two classes of a-zeins, 219 and 222, were in good agreement with the ahelical contents determined by circular dichroism. Dimensions determined by small angle x-ray scattering and viscometry indicated a predominantly a-helical conformation. The data are discussed in relation to models for the solution conformation and to earlier models for a-zeins structure. The alcohol soluble zein storage proteins (prolamins) of maize (Zea mays) are a mixture of proteins and constitute about 50-60% of total endosperm protein. Their only known function is to act as a store of nitrogen for the developing seed. The zeins are rich in glutamine, proline, and unlike other cereal prolamins from wheat, barley and rye, in leucine and alanine. The zeins are separated into four classes, a-, p-, y-, and 6-, on the basis of differences in solubility and sequence (1). The a-zeins constitute 75-85% of the total fraction and comprise two protein groups, the Z19 and 222 zeins, with molecular masses by SDS-PAGE' of about 19 and 22 kDa, respectively. Analysis by isoelectric focusing indicates the azeins to be a heterogeneous mixture of up to 15 proteins (2). A number of complete a-zeins sequences have been deduced from cloned cDNAs and genes (3, 4), showing that the Z19 and 222 components consist of about 210 and 245 residues, with true molecular weights of about 23,000-24,000 and 26,000-27,000, respectively. The sequences show unique Nand C-terminal domains of about 36-37 and 10 residues, respectively, separated by a repetitive domain consisting of blocks of between about 14 and 25 residues (with an average length of 20 residues). The size difference between the Z19 and 222 zeins results from the insertion of an additional repeat unit in the C-terminal end of the protein. This insertion gives a total of 10 repeats in the 222 zeins compared with 9 in the 219 zeins. The p-, y-and 6-zeins show no sequence homology with the a-zeins. Although the pand 6-zeins do not contain repeated sequence motifs, which is unusual for
Absence of storage protein synthesis in the embryo of Zea mays
Plant Science, 1987
Polypeptides were identified in the total protein extract from isolated maize embryos having a similar behaviour of endosperm zeins and glutelins by means of two-dimensional gel electrophoresis. They reacted with antisera ellicited against the same proteins as seen by immunoblotting. In contrast, mRNAs coding for these proteins were not identified in the poly(A +) or poly(A-) RNA fractions prepared from embryo tissues by Northern hybridization experiments or immunoprecipitation of the in vitro translated products. 'In situ' hybridization experiments with zein cDNA clearly show that the corresponding mRNAs are confined to the endosperm and they are not present in the embryo tissues. Possible hypotheses to explain these results are discussed.
The EMBO journal, 1989
The structure of the zein regulatory gene Opaque 2 of Zea mays has been determined by sequence analysis of genomic and cDNA clones. The size of O2 mRNA is 1751 bp [poly(A) tail not included] containing a major open reading frame (ORF) of 1380 bp preceded by three short ORFs of 3, 21 and 20 amino acid residues. The main ORF comprises 1362 bp and is composed of six exons ranging in size from 465 to 61 bp and five introns of 678 bp to 83 bp. A putative protein 454 amino acids long was derived by the theoretical translation of the genomic sequences corresponding to exons. The opaque 2 protein contains a domain similar to the leucine zipper motif identified in DNA binding proteins of animal protooncogenes such as fos, jun and myc, and in the transcriptional activators GCN4 and C/EBP. The region of 30 amino acid residues next to the leucine repeats towards the N terminus is rich in basic amino acids and is also homologous to a domain present in fos, jun and GCN4. Moreover, in the carboxy ...
MGG Molecular & General Genetics, 1987
The nucleotide sequence of gzl9abll, a clone that corresponds to the coding and flanking sequences of an Mr 19000 alpha zein, was determined. Comparison of the DNA sequences flanking this gene with those of other members of the gene subfamily showed that sequence conservation extends 820 nucleotides into the 5' flanking region and 130 nucleotides into the 3' flanking region. Southern blot analysis of maize DNA indicated that highly repetitive sequences are located within 950 bp 5' and 300 bp 3' to the protein coding region of these genes. The coding region of gzl9abll is similar to but not identical with cDNA clones corresponding to Mr 19000 zeins, and analysis of zein transcripts indicated that this gene is expressed exclusively in endosperm tissue. RNAs which correspond to transcripts originating 60 nucleotides, and more than 800 nucleotides, upstream of the initiation codon were detected for this and a related gene. However, the concentration of the large RNA species was several orders of magnitude less than that of the shorter RNAs. The functional significance of these large RNA transcripts in zein gene expression is unclear.
Role of structural domains for maize ?-zein retention in Xenopus oocytes
Planta, 1994
In order to examine the role of cysteine (Cys)rich domains in the accumulation of maize (Zea mays L.) 7-zein within the endoplasmic-reticulum-derived protein bodies, we studied the localization of 7-zein and of two truncated forms of 7-zein in Xenopus laevis oocytes. The two derivatives were constructed from a DNA encoding the 7-zein: one by deletion of the Pro-X linker region (21 amino acids) and the other by deletion of the Cys-rich domain (94 amino acids). In-vitro-synthesized transcripts were injected into oocytes and the distribution of the translation products was then analyzed. The entire 7-zein and both truncated forms of the 7-zein had accumulated efficiently in microsomes and no traces of secretion were observed. We suggest that neither C-terminal Cys-rich nor Pro-X domains are essential for 7-zein retention in oocyte vesicles. Therefore, structural features derived from disulphide bonds are not necessary for 7-zein targeting on the endoplasmic reticulum.
Genes for zein subunits on maize chromosone 4
Biochemical Genetics, 1982
This paper maps nine genes coding for zein subunits on maize chromosome 4. Six of them (Zp6h, Zpl0, Zpl4, Zpl5, Zp22) encode for subunits with a molecular weight of 22 Kd (kilodaltons), while three (Zp27, Zp28, Zp30) code 20-kd subunits. The six 22-kd related genes are not contiguous but are scattered on both chromosome arms, whereas Zp27, Zp28, and Zp30 are more tightly linked in the chromosome short arm in a segment 5 crossover units long. The organization of zein genes on chromosome 4 shows a close analogy with that of zein loci on chromosome 7. This suggests that both maize chromosomes evolved by duplication of short segments.
Chromosomal localization of zein genes by in situ hybridization in Zea mays
MGG Molecular & General Genetics, 1980
In order to localize the genes coding for zein, the major storage protein of maize endosperm, zein 125I-mRNA and 3H-cDNA labelled at high specific activity were used for in situ hybridization on heterozygous interchanges and paracentric inversions of the KYS strain of Zea mays. The analysis of the diplotene-metaphas e I microsporocytes indicated the presence of zein structural genes on the long arm of chromosomes 4 and 5, the short arm of chromosome 7 and the distal segment of the long arm of chromosome 10. The two hybridization sites on chromosomes 7 and 10 are found near opaque-2 and opaque-7 loci which are known to regulate zein synthesis. The present data are discussed in relation to results obtained by other authors using genetical mapping of zein genes.