title: The effect of starvation stress on Lactobacillus brevis L62 protein profile determined by de novo sequencing in positive and negative mass spectrometry ion mode.
abstract: BACKGROUND
  We describe a novel negative chemically activated fragmentation/positive chemically activated fragmentation (CAF-/CAF+) technique for protein identification. The technique was used to investigate Lactobacillus brevis adaptation to nutrient deprivation.
  
  
  METHODS
  The CAF-/CAF+ method enables de novo sequencing of derivate peptides with negative and positive ion mode matrix-assisted laser desorption/ionization (MALDI) tandem mass spectrometry (MS/MS). Peptide sequences obtained from MS/MS spectra were matched against the National Center for Biotechnology Information (NCBI) non-redundant (nr) database and confirmed by the mass spectrometry data of elucidated peptide mass sequences derived from the annotated genome. This improved protein identification method highlighted 36 differentially expressed proteins in the proteome of L. brevis after 75 days of starvation.
  
  
  RESULTS
  The results revealed the key differences in the metabolic pathways that are responsible for the survival of L. brevis in a hostile environment. Proteomics analysis demonstrated that numerous proteins engaged in glucose and amino-acid catabolizing pathways, glycerolipid metabolizing pathways, and stress-response mechanisms are differentially expressed after long-term starvation. Amino acid and proteomics analysis indicated that starved L. brevis metabolized arginine, glycine, and histidine from dead cells as alternative nutrient sources. The production of lactic acid also varied between the parent cells and the starved cells.
  
  
  CONCLUSIONS
  Differentially expressed proteins identified exclusively by peptide sequence reading provided promising results for CAF-/CAF+ implementation in a standard proteomics workflow (e.g., biomarker and mutation discovery and biotyping). The practical performance of a reliable de novo sequencing technique in routine proteomics analysis is emphasized in this article.
authors.affiliation: Faculty of Food Technology and Biotechnology, University of Zagreb, Zagreb, Croatia.
authors.forename: Ana
authors.initials: A
authors.lastname: Butorac
authors.forename: Ivana
authors.initials: I
authors.lastname: Dodig
authors.forename: Višnja
authors.initials: V
authors.lastname: Bačun-Družina
authors.forename: Arye
authors.initials: A
authors.lastname: Tishbee
authors.forename: Jasna
authors.initials: J
authors.lastname: Mrvčić
authors.forename: Karlo
authors.initials: K
authors.lastname: Hock
authors.forename: Janko
authors.initials: J
authors.lastname: Diminić
authors.forename: Mario
authors.initials: M
authors.lastname: Cindrić
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis / Q000378:metabolism*; D052196:Levilactobacillus brevis / Q000502:physiology*; D040901:Proteomics / Q000379:methods; D020539:Sequence Analysis, Protein / Q000379:methods; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D053719:Tandem Mass Spectrometry / Q000379:methods
chemical_list: D001426:Bacterial Proteins