2Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, 117991 Moscow, Russia; fax: (495) 335-7103
3Institute for Automation and Control Processes, Far East Division of the Russian Academy of Sciences, ul. Radio 5, 690041 Vladivostok, Russia
* To whom correspondence should be addressed.
Received August 12, 2008; Revision received November 27, 2008
A low-molecular-weight cationic protein that can bind human and rabbit immunoglobulins G has been isolated from Yersinia pseudotuberculosis cells. This immunoglobulin binding protein (IBP) interacts with IgG Fc-fragment, the association constant of the resulting complex being 3.1 µM–1. MALDI-TOF mass spectrometry analysis of IBP revealed its molecular mass of 16.1 kDa, and capillary isoelectrofocusing analysis showed pI value of 9.2. N-Terminal sequence determination by Edman degradation revealed the sequence of the 15 terminal amino acid residues (ADKIAIVNVSSIFQ). Tryptic hydrolysate of IBP was subjected to MALDI-TOF mass spectrometry for proteolytic peptide profiling. Based on the peptide fingerprint, molecular mass, pI, and N-terminal sequence and using bioinformatic resources, IBP was identified as Y. pseudotuberculosis periplasmic chaperone Skp. Using the method of comparative modeling a spatial model of Skp has been built. This model was then used for modeling of Skp complexes with human IgG1 Fc-fragment by means of molecular docking.
KEY WORDS: chaperone Skp, immunoglobulin-binding protein, immunoglobulin G, Fc fragment of IgG, computer modeling