Table 1. Biotinylated surface-exposed proteins of R. rickettsii analyzed by ESI-MS/MS.

Spot NO	Annotation	Accession numbersa	Signal peptideb (position)	Scores for β-barrelc	MW(Da)	Scored	Predicted function	Pfam familye
10,11	Adr1	A1G_07045	YES (22,23)	2.818	26486	369	Cell envelope biogenesis, outer membrane	PF12393
7,8	Adr2	A1G_07050	YES (22,23)	2.836	24083	355	Cell envelope biogenesis, outer membrane	PF12393
1	DNA-binding protein	A1G_06785	NO	2.979	16102	115	Adsorption capacity and tendency to small nucleotide fragments	PF00210
20,21,22,23	GroEL	A1G_05320	NO	2.886	58590	1133	60 kDa heat shock protein (Hsp60)	PF00118
2,4,5,6	GroES	A1G_05325	NO	3.049	10515	495	10 kDa heat shock protein (Hsp10)	PF00166
17,18,19	Porin_4	A1G_00605	YES (19,20)	2.882	48023	1084	Molecular sieve	PF13609
12	OmpA	A1G_06990	NO	2.873	224236	211	Invasion and adhesion	PF03797
13,14,15	Omp B	A1G_06030	YES (29,30)	2.868	168082	387	Invasion and adhesion	PF03797
9	OmpW	A1G_00640	YES (23,24)	2.911	26509	140	Transportation of hydrophobic material across cell membrane	PF03922
16	TolC	A1G_01745	YES (19,20)	2.916	49691	90	Outer membrane efflux proteins	PF02321

^aThe National Center for Biotechnology Information (NCBI, http://www.ncbi.nlm.nih.gov/). Data were retrieved on March 4, 2013.

^bThe signal peptide was predicted using SignalP 4.1 web server (http://www.cbs.dtu.dk/services/SignalP/). Websites were accessed on March 4, 2013.

^cThe transmembrane strands and the topology of beta-barrel outer membrane proteins of R. rickettsii were predicted using the PRED-TMBB web server (http://bioinformatics.biol.uoa.gr/PRED-TMBB), which is based on a Hidden Markov Model, trained according to the Conditional Maximum Likelihood criterion. A score less than 2.965 indicated that the protein may be a membrane protein. Data were retrieved on March 7, 2013.

^dThe ions score is presented as -10*Log (P), where P is the probability that the observed match is a random event. Individual ions scores >54 indicate identity or extensive homology (P<0.05). Protein scores are derived from ions scores on a non-probabilistic basis for ranking protein hits.

^eThe Pfam-A was used to predict the family of the protein, Pfam does not allow any amino-acid to match more than one Pfam-A family(http://pfam.sanger.ac.uk/), unless the overlapping families are part of the same clan. In cases where two members of the same clan match the same region of a sequence, only one match is show, that with the lowest E-value. The E-value cut-off in Pfam-A search was set to 1.0. Data were retrieved on July 19, 2013.