Characterization of the kafirin gene family from sorghum reveals extensive homology with zein from maize

Abstract

Electrophoretic analysis of translation products of polyadenylated RNA isolated from mid-maturation sorghum seed in the presence of [(35)S]met, [(3)H]leu, or [(3)H]val revealed two major proteins of kDa and 21 kDa. These products were not detected when [(3)H]lys was supplied as the radioactive substrate. Under similar electrophoretic conditions, kafirin (a major seed storage prolamin of sorghum), migrated as two bands of 22 kDa and 19 kDa. Sequence analysis of two cDNA clones (pSK8 and pSKR2) from sorghum seed mRNA revealed them to be highly homologous with each other and to the 22 kDa zeins from maize, suggesting that they represented kafirin cDNAs. Compared with pSKR2, pSK8 had an insertion of 24 nucleotides and a deletion of 24 nucleotides, so that the coding regions were nearly identical in length. The deduced amino acid sequence for these cDNA clones reveals that kafirin, like zein, is rich in glutamine and nonpolar amino acids, but contains no lysine. Both kafirin and zein have a 21 amino acid signal peptide exhibiting 80% homology and eight copies of a repetitive amino acid block in the C-terminal domain with the consensus: infI (supP) LL finP (supA) LN infQ (supP) LALANPAAYLQQQQ.The kafirin cDNAs were used as probes to screen a sorghum genomic library; one genomic clone (λGK.1) was sequenced and found to be very similar (97.8%) to the pSK8 cDNA clone. Clone λGK.1 contains features typical for a functional gene in that the intronless open reading frame encoding 268 amino acids is flanked at the 5' end by sequences corresponding to the CAAT and TATA promoter boxes (positioned at about -60 and -30 bp, respectively, from the transcriptional initiation site), and at the 3' end by a consensus polyadenylation signal. In common with zein genomic clones, kafirin clones contain a 15 basepair consensus sequence centered at postion -320 relative to the transcriptional initiation site. Under similar hybridization conditions, genomic reconstruction analysis using an oligonucleotide probe indicated the presence of less than 20 copies of kafirin per haploid sorghum genome compared with approximatley 140 copies of zein per haploid maize genome.

Biocompatibility and biodegradation of protein microparticle and film scaffolds made from kafirin (sorghum prolamin protein) subcutaneously implanted in rodent models

“…Macroscopic and histological evaluation showed no abnormal pathology for any of the organs from rats implanted with any of the treatments at both time intervals. Overall, the data showed that kafirin microparticle film implants, including films treated with glutaraldhyde, sorghum polyphenols or rhBMP-2 were non-irritant to the rats, agreeing with studies showing that zein, which is homologous to kafirin, 11 has good cell compatibilitl· 30 and has shown no adverse effects when used as a scaffold material in animal studies.…”

“…6 Zein has been shown to have good bio-and cyto-compatibility. 7 In vivo studies of zein scaffolds have shown good tissue response and biodegradability 8 • 9 Further, complexes of zein scaffolds and rabbit mesenchymal stem cells have been shown to undergo ectopic bone formation in the thigh muscle pouches of nude mice, 10 Kafirin is the homologous sorghum protein to zein, 11 and may have some advantages over zein for use in biomedical applications. Kafirin is usually considered more hydrophobic/ 2 is less digestible, 12 and has a higher glass transition temperature than zein.…”

Mosaic Organization of Orthologous Sequences in Grass Genomes

“…Interestingly, 22 members are tandemly arrayed within 168 kb, whereas one copy is located 20 cM closer to the centromere of maize Chromosome 4S. Sorghum also has a storage protein, 22-kD kafirin, homologous to the maize 22-kD zein (DeRose et al 1989). Rice does not have a corresponding storage protein (Kim and Okita 1988).…”

A maize α-zein promoter drives an endosperm-specific expression of transgene in rice

“…Schmidt et al (1992) suggested that O2 may interact with factors binding the P-box to activate 22-kDa zein gene expression. It was reported that 7 bp P-box sequence was common in cereals like oats (Shotwell et al 1990), wheat (Colot et al 1987), barley (Marris et al 1988), and sorghum (DeRose et al 1989) and plays a key role in regulating the endospermspecific expression.…”