Destabilization of C_H2 Domains in Intact IgG2 Is Accompanied by Reduced Ability to Inhibit Complement System Factor C1

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M. A. Timchenko and V. M. Tischenko^*

Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Institutskaya ul. 3, 142290 Pushchino, Moscow Region, Russia; fax: (4967) 33-0553; E-mail: tischen@vega.protres.ru

^* To whom correspondence should be addressed.

Received January 23, 2013; Revision received March 14, 2013

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Fc fragments (hFc) of human myeloma IgG2 proteins LOM and SIN having core hinge (Cys-Cys-Val-Glu-Cys-Pro-Pro-Cys) were first obtained by a modified proteolytic procedure. The thermostability of C_H2 domains inside of standard Fc, hFc fragments, and intact IgG2 LOM and SIN was studied by fluorescence spectroscopy. It was found that C_H2 domains of intact IgG2 are destabilized. The destabilization is accompanied by reduced ability of IgG2 to inhibit the activation of complement system by classical pathway. This could be due to the decrease in the affinity of C_H2 domains to factor C1q.

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KEY WORDS: immunoglobulin IgG2, Fc fragment, C_H2 domain, complement system factor C1q, myeloma, stability

DOI: 10.1134/S0006297913060126

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