Detection and characterization by high-performance liquid chromatography and mass spectrometry of a goat beta-casein associated with a CSN2 null allele.
The identification and characterization of a truncated goat beta-casein, associated with a null beta-casein allele (CSN2(O')), is reported. The truncated beta-casein predicted at the DNA level (NCBI Acc. No. CAB39313) but never observed at the protein level, here named beta-casein O, was detected as a minor component in a goat milk sample from an autochthonous breed from southern Italy, 'Rossa Mediterranea', by reversed-phase high-performance liquid chromatography/electrospray ionization mass spectrometry (RP-HPLC/ESI-MS). The ESI mass spectrum of the intact beta-casein O determined an M(r) value of 18 780 Da (calculated 18 781.5). Characterization of the amino acid sequence, performed by coupling trypsin digestion with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), RP-HPLC/ESI-MS and tandem mass spectrometry (MS/MS), demonstrated that the amino acid sequence corresponds to the 1-166 sequence of mature beta-casein variant A (Acc. No. P33048), thus confirming that the protein is coded by the null allele CSN2(O'), characterized by a transition (C --> T) at the 373rd nucleotide of the 7th exon of the gene, which generates a premature stop codon in position 182.
Cunsolo
Vincenzo
V
Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale A. Doria, 6, 95125 Catania, Italy.
Galliano
Francesco
F
Muccilli
Vera
V
Saletti
Rosaria
R
Marletta
Donata
D
Bordonaro
Salvatore
S
Foti
Salvatore
S
D000483:Alleles; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D002364:Caseins / Q000032:analysis / Q000737:chemistry* / Q000235:genetics*; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D004252:DNA Mutational Analysis / Q000379:methods; D006041:Goats; D013058:Mass Spectrometry / Q000379:methods*; D008894:Milk Proteins / Q000032:analysis / Q000737:chemistry* / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D010449:Peptide Mapping / Q000379:methods; D020539:Sequence Analysis, Protein / Q000379:methods*
D002364:Caseins; D008894:Milk Proteins