Proteomic analysis of Yersinia enterocolitica biovar 1A under iron-rich and iron-poor conditions indicate existence of efficiently regulated mechanisms of iron homeostasis Pawan Kumar Kanaujia a, 1 , Priyanka Bajaj a, 1 , Shakti Kumar b , Neelja Singhal a , Jugsharan Singh Virdi a, ⁎ a Microbial Pathogenicity Laboratory, Department of Microbiology, University of Delhi South Campus, Benito Juarez Road, New Delhi 110 021, India b Parasitology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong 793022, India ARTICLE INFO ABSTRACT Article history: Received 24 January 2015 Accepted 13 April 2015 Available online 23 April 2015 The pathogenicity of Yersinia enterocolitica biovar 1A strains is controversial as these lack most of the known virulence factors. Acquisition of iron and presence of well-regulated iron homeostasis in bacteria represents an important virulence trait. Differential abundance of proteins was examined under iron-rich and iron-poor conditions in a clinical Y. enterocolitica biovar 1A strain IP27407. Whole cell protein profiles were analysed by 2D gel electrophoresis (2D-GE). Following statistical and MALDI-TOF MS analyses, 28 differentially abundant proteins were identified. Significant iron-responsive changes were observed in the proteins involved in iron acquisition or storage namely, hemin receptor (HemR), periplasmic Fe 2+ transport protein (Tpd), periplasmic chelated iron-binding protein (YfeA) and bacterioferritin (Bfr). Quantitative real-time PCR (qRT-PCR) of eight mRNA transcripts revalidated the differential protein abundance. In silico analysis of iron homeostasis mediated by the bacterioferritin and bacterioferritin-associated ferredoxin (Bfr–Bfd) complex suggested two pathways for the release of reserve iron which might be operating under conditions of different iron availability. The study, for the first time, showed the existence of highly competent iron homeostasis mechanisms in Y. enterocolitica biovar 1A and identified the key proteins involved thereof. Such mechanisms might have implications for the pathogenicity of Y. enterocolitica biovar 1A strains. Biological significance Although, a few studies have identified the differentially abundant bacterial proteins in response to iron starvation, little information is available in this regard for Y. enterocolitica (especially, the biovar 1A strains). In the present study, differential abundance of several proteins was identified under iron-rich and iron-poor conditions by 2D-GE and MALDI-TOF/ MS analysis. These included proteins which may not only be directly implicated in iron acquisition or storage but also play crucial role in cellular metabolism. Given the absence of most known virulence factors in Y. enterocolitica biovar 1A strains, demonstration of Keywords: Bfr–Bfd 2D gel electrophoresis Iron MALDI-TOF MS Proteomic Y. enterocolitica biovar 1A JOURNAL OF PROTEOMICS 124 (2015) 39 – 49 ⁎ Corresponding author. E-mail addresses: pkkanaujia@gmail.com (P.K. Kanaujia), bajaj.priyanka06@gmail.com (P. Bajaj), kumar4ushakti@gmail.com (S. Kumar), neelja30@gmail.com (N. Singhal), virdi_dusc@rediffmail.com (J.S. Virdi). 1 Equal contributors. http://dx.doi.org/10.1016/j.jprot.2015.04.015 1874-3919 © 2015 Elsevier B.V. All rights reserved. Available online at www.sciencedirect.com ScienceDirect www.elsevier.com/locate/jprot