The protein and peptide fractions of kashk, a traditional Middle East fermented dairy product.

Kashk is a typical dairy product of Iran, made from sour milk. It is traditionally produced from buttermilk in a dry, round-shaped form. Today, it is also produced at industrial level in a liquid form starting from fermented milk. We aimed to characterise the kashk proteome and peptidome comparing a traditional product with the industrial using a combination of proteomic approaches including advanced chromatographic and electrophoretic separation technique coupled to tandem mass spectrometry. We identified also phosphorylated casein-derived peptides (CPP) and investigated kashk protein digestibility using a static model of food protein digestion. The molecular characterization, coupled with bioinformatic in silico analysis, allowed the identification of potential bioactive peptides.

Casein composition and differential translational efficiency of casein transcripts in donkey's milk.

The amount of the four caseins (αs1, αs2, ß and κ-CN) in donkey milk was evaluated by Urea-PAGE analysis at pH 8.6, followed by immuno-detection with polyclonal antibodies, coupled to densitometric analysis. The results showed the percentage of each casein in decreasing order: ß (54.28) > αs1 (35.59) > αs2 (7.19) > κ-CN (2.79). The mRNA quantification of donkey casein transcripts, carried out by RT-qPCR, showed that the average percentage of corresponding gene transcripts (CSN2, CSN1S1, CSN1S2 I and CSN3) was 70.85, 6.28, 14.23 and 8.65, respectively. The observed translation efficiency, assessed as percentage of single milk casein fraction out of single percentage of transcript, was 0.76, 5.66, 0.50 and 0.32, respectively. The analysis of the sequences flanking the start codon, the codon usage frequencies and the coding sequence length might explain, at least in part, the differential transcriptional and translational rate observed among the casein transcripts.

Profiling of anthocyanins for the taxonomic assessment of ancient purebred V. vinifera red grape varieties.

For the purpose of a varietal assessment, the berry skin anthocyanin profiles of 11 ancient native red grape varieties, sampled within the Irpinian area (Southern Italy), were compared to those of three reference Vitis vinifera cultivars and of a Kober 5BB rootstook hybrid (Vitisberlandieri×Vitisriparia). The 3,5-O-diglucoside anthocyanins and their acylated derivatives were monitored as signature compounds of non-V. vinifera grapes, using both reversed phase-high performance liquid chromatography (RP-HPLC) and matrix assisted laser desorption ionisation-time of flight (MALDI-TOF) mass spectrometry (MS). One variety (i.e. Tenta) was demonstrated to be an interspecific hybrid cross. Three additional varieties, namely Lacrima Nera, Aglianicone and a yet-unnamed variety, were classified as "late generation hybrids" (or non-V. vinifera×V. vinifera hybrids) because of a very diluted hybrid character, that was revealed only by MS methods. Five cultivars, i.e. Aglianico Lasco, Cannella, Coda di Volpe Rossa, Mentuonico, Olivella Nera, were catalogued as purebred V. vinifera. Due to the peculiar anthocyanin profile one variety (Tuccanese) remained unassigned. The methodology is of general applicability to support the process of varietal discrimination on a molecular basis with the objective of classifying autochthonous old grapevine varieties.

The occurrence of genetic polymorphism and related non-allelic proteins increases the compositional complexity of goat α((s1)) -CN.

A genetic survey on three autochthonous goat breeds reared in Italy was carried out by a proteomic approach. This methodology, further to providing the phenotypic frequency of identified α(s1) genetic variants, allowed to determine (i) the additional constitutive presence of a non-allelic 'α(s1) -casein (CN) F like' protein in goat 'strong' α(s1) variants; (ii) an α(s1) -CN B(2) like protein, expressed at very low quantitative level, in goat 'weak' α(s1) -CN variants, and, as main focus; (iii) the occurrence of a new α(s1) -CN D(1) variant characterised by the lack of α(s1) (f59-69) sequence otherwise encoded by exon 9 in goat α(s1) B(2) reference. The same exon skipping event had been identified since 1990, as responsible of the 'weak quantitative class' of α(s1) -CN D variant (0.6 g/L), while the new α(s1) -CN D(1,) has been 'quantitatively' classified as an 'intermediate' variant, since 1.8 g/L per allele was assessed in the milk.

Proteomic characterization of donkey milk "caseome".

At present, compared with bovine milk, the characterization of donkey milk caseins is at a relatively early stage progress, and only limited data are related to its genetic polymorphism. In this work, the heterogeneity of donkey caseome was investigated using a proteomic approach, based on one- (PAGE, UTLIEF) and two-dimensional (PAGE-->UTLIEF) electrophoresis, stained with either Coomassie Brilliant Blue or specific polyclonal antibodies, and structural MS analysis. These combined methodologies allowed the contemporary identification of donkey alpha(s1), alpha(s2), beta and kappa-CN with their related heterogeneity due to phosphorylation (alpha(s1), alpha(s2) and beta-CN), glycosylation (kappa-CN) and incorrect splicing of RNA in mRNA (deleted forms of alpha(s1)-CN and beta-CN). The results achieved showed 11 components for kappa-CN, six phosphorylated components for beta and alpha(s1)-CN and three main phosphorylated components for alpha(s2)-CN, each accounting for 10, 11 and 12 P/mole. At this regard, for the first time, the primary structure of the expressed protein corresponding to the only available donkey alpha(s2)-CN cDNA sequence was determined. Furthermore beta-CN was found in homozygous and heterozygous state for the occurrence of a genetic beta-CN variant having a MW value 28 mass units higher than the common beta-CN phenotype.

Casein phosphoproteome: identification of phosphoproteins by combined mass spectrometry and two-dimensional gel electrophoresis.

We report a fast and easy-to-use procedure that combines polyacrylamide gel electrophoresis with matrix assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF) and nanoelectrospray-tandem mass spectrometry (nES-MS/MS) analysis for the identification of casein components and defined phosphorylated sites. This methodology ensured identification of more than 30 phosphorylated proteins, five beta-, fifteen alpha(s1)-, ten alpha(s2)-, and four kappa-casein (CN) components, including nonallelic, differently phosphorylated, and glycosylated forms. The sugar motif covalently bound to kappa-CN was identified as chains, trisaccharide GalNAc, Gal, NeuGc, and tetrasaccharide 1GalNAc, 1Gal, 2NeuGc. Also identified was a biantennary chain made up of both chains of trisaccharide 1GalNAc, 1Gal, 1NeuGc, and tetrasaccharide 1GalNAc, 1Gal, 2NeuGc moiety on a single kappa-CN component. The phosphate group on site Ser12 of tryptic peptide 8-22 of most phosphorylated alpha(s1)-CN (11 phosphate groups) was localized and the oligosaccharide sequence of the main tryptic glycopeptides of two kappa-CN components was determined by means of MS/MS analysis.

Interallelic recombination is probably responsible for the occurrence of a new alpha(s1)-casein variant found in the goat species.

The alphas1-casein (alphas1-Cas) locus in the goat is characterized by a polymorphism, the main feature of which is to be qualitative as well as quantitative. A systematic analysis performed in an autochthon southern Italy breed identified a new rare allele (M), which was characterized at both the protein and genomic level. The M protein displays the slowest electrophoretic mobility of the alphas1-Cas variants described so far. MS and automated Edman degradation experiments showed that this behavior was due to the loss of two phosphate residues in the multiple phosphorylation site (64SP-SP-SP-SP-SP-E-70E) consecutively to a Ser-->Leu substitution at position 66 of the peptide chain (64S-SP-L-SP-SP-E-70E). This was confirmed by sequencing a genomic DNA fragment encompassing exon 9 where the 8th codon (TCG) was shown to be mutated to TTG. Sequencing of amplified genomic DNA segments spanning the 5' and 3' flanking regions of each exon allowed us to identify 23 single nucleotide polymorphisms and two insertion/deletion events in the coding as well as the noncoding regions. A comparison of specific haplotypes defined for each of the alphas1-CasF, A and M alleles indicates that the M allele probably arises from interallelic recombination between alleles A and B2, followed by a C-->T transition at nucleotide 23 of the ninth exon. The region encompassing the recombination break point was putatively located between nucleotide 86 upstream and nucleotide 40 downstream of exon 8. Interallelic recombination therefore appears to be a possible means of generating allelic diversity at the alphas1-Cas locus, at least in the goat. The previously proposed molecular phylogeny must now be revised, possibly starting from two ancestral allelic lineages.