A cross‐species quantitative proteomic study of salt adaptation in a halotolerant environmental isolate using ¹⁵N metabolic labelling

Abstract

We examine differential protein expression in Euhalothece sp. BAA001, an extremely halotolerant and unsequenced cyanobacterium, under adaptation to low (0% w/v), medium (3% w/v), high (6% w/v) and very high (9% w/v) salt concentrations using cross-species protein identification tools. We combine stable isotope labelling with 1-D SDS-PAGE, and MASCOT protein identification software with MS-driven BLAST searches, to produce an accurate method for protein identification and quantitation. The use of metabolic labelling to improve the confidence in identification of proteins in cross-species proteomics is demonstrated. Three hundred and eighty-three unique proteins were identified, and 72 were deemed to be differentially expressed (average CV for quantitations was 0.10 +/- 0.08), belonging to 24 functional groups. Responses to low salt as well as high salt are discussed in terms of adaptation and evidence shows that Euhalothece cells display 'stress' responses in nonsaline conditions as well as higher salt environments.

Interplay of adaptive capabilities of Halomonas sp. AAD12 under salt stress

“…Recycling of EF-Tu-GDP to EF-Tu-GTP is catalyzed by a guanine-nucleotide exchange factor, EF-Ts (54). Increase in the expression of both EF-Ts and EF-Tu with salinity in different bacteria could be found in literature (12,41,48). It has been suggested that EF-Tu and EF-Ts might also play a role in protein folding and/or protection from stress since they show chaperone like properties (55e57).…”

Molecular biology of cyanobacterial salt acclimation

“…In these studies, the proteins were analyzed by peptide-mass-fingerprinting using MALDI-TOF MS and the quantification was based on quantitative evaluation of stained protein spots. BAA001, could be analyzed using the genome information from Synechocystis 6803 (Pandhal et al, 2008a(Pandhal et al, , b, 2009b. However, the gelbased technology has limitations, especially in the coverage of membrane-bound or alkaline proteins.…”

Quantitative proteomic analysis of intracytoplasmic membrane development in Rhodobacter sphaeroides

“…Although arguably less popular than in vitro chemical isotopic labelling (for example see Jain et al ., 2011) metabolic stable isotopic labelling is widely recognized as a robust method for accurate relative quantification (Whitelegge et al ., 2004; Elliott et al ., 2009). For example, this labelling protocol has been used to investigate salt adaptation in the cyanobacteria Synechocystis and Euhalothece (Pandhal et al ., 2008; 2009). The application of this method to the comparative quantification of UPB and ICM proteins shows the selective enrichment of proteins involved in light harvesting and energy transduction in the ICM, with concomitant exclusion of, for example, proteins involved in carbohydrate and amino acid metabolism.…”