Oral Presentation 10th Modern Solid Phase Peptide Synthesis & Its Applications Symposium 2025

Effect of deamidation on the fibril formation of β2-microglobulin   (129584)

Ryuji Kawakami 1 , Toshiki Takei 1 , Toshifumi Takao 1 , Masatomo So 2 , Hironobu Hojo 1
  1. Institute for Protein Research, The University of Osaka, Osaka, Japan
  2. Graduate School of Agriculture, Kyoto University, Kyoto

 

β2-microglobulin (β2m) is a component of the major histocompatibility complex class I molecules. Although the blood concentration of β2m in healthy person is maintained low, in the case of dialysis patients with impaired renal function,b2m cannot be effectively metabolized and also not eliminated by the dialysis. As a result, β2m accumulated in the body gradually forms fibrous aggregates that are deposited in joints and other areas, causing the dialysis related amyloidosis (DRA). However, the detailed mechanism of β2m amyloid  formation is not known in detail and no fundamental treatment has been established. One of the causes of DRA is thought to be the D6N mutant, which lacks the N-terminal six amino acid residues and often found in the amyloid deposits of DRA patients. This mutant has an enhanced amyloid fibril formation ability compared to the native β2m.

              Recently, the deamidated β2m has also been found in the amyloid deposits of DRA patients and suggested to be one of the causes of amyloid fibril formation. The deamidation reaction often occurs at Asn-Gly sequence in polypeptides and results in the sequence conversion to Asp-Gly or isoAsp-Gly. In the b2m sequence, there are Asn17-Gly18 and Asn42-Gly43 sequences. In this study, we chemically synthesized the deamidated β2ms to clarify their structure and property. Based on the deamidation ratios in previous studies [1], we synthesized five deamidated β2m, with the 17th amino acid being Asn, Asp, and isoAsp, and the 42nd amino acid being Asn and isoAsp.

              The entire sequence of β2m was divided into three segments at the N-terminus of Cys25 and Cys80 residues and each peptide segment was synthesized by the solid-phase method. For the N-terminal segment, Asn, Asp, or isoAsp was introduced as the 17th residue. In a similar manner, two segments with Asn or isoAsp at 42nd residue were synthesized for the middle segments. After obtaining required segments, the native chemical ligation reaction [2] was performed to obtain five b2m variants. In this presentation, the results of the synthesis and their aggregation property will be reported.

 

  1. M. Fukuda, T. Takao, Anal. Chem., 2012, 84, 10388-10394.
  2. P. E. Dawson, T. W. Muir, I. Clark-Lewis, S. B. H. Kent, Science, 1994, 266, 776-779.