Intra -strain variability in the amino acid sequence of S-layer proteins from Lactobacillus kefiri

MALAMUD M; CARASI P; SERRADELL MA

Córdoba

Congreso; LII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2016

SAIB

Bacterial S-layers are proteinaceous crystalline arrays composed of self-assembling glycoprotein subunits called S-layer proteins (SLPs). Previous mass spectrometry analysis showed a great structural heterogeneity among SLP from aggregative and non-aggregative strains of Lactobacillus kefiri, a potentially probiotic microorganism. Some of them share several fragments with the SLP from phylogenetically related lactobacilli. Based on this information, specific primers located outside and inside the SLP-genes were designed in order to amplify genomic DNA. Ten strains were selected for sequencing of the complete genes. The glycosylation site SSASSASSA was found in all L. kefiri SLPs, whereas cysteine is absent. The total length of the proteins varies from 492 to 576 amino acids, and all SLPs have a high calculated pI (9.37-9.60). N-terminal region is relatively conserved and shows a high percentage of positively charged amino acids. Major differences among strains are found in the C-terminal region. Different groups could be distinguished regarding the amino acid sequences and the similarities observed in mass spectra. Interestingly, SLPs of the aggregative strains CIDCA 8321, 8348 and 83115 are 100% homologue, although were isolated from different kefir grains. This knowledge will contribute to the development of products of biotechnological interest from potentially probiotic bacteria.