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Int J Mol Sci. 2019 Oct 20;20(20). pii: E5197. doi: 10.3390/ijms20205197.

Effect of Single Amino Acid Substitutions by Asn and Gln on Aggregation Properties of Bence-Jones Protein BIF.

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Laboratory of NMR of Biosystems, Institute of Theoretical and Experimental Biophysics RAS, Pushchino 142290, Russia.
Laboratory of Biotechnology and Physiology of Phototrophic Organisms, Institute of Basic Biological Problems RAS-a separate subdivision of PSCBR RAS (IBBP RAS), Pushchino 142290, Russia.
Himeji-Hinomoto College, 890 Koro, Kodera-cho, Himeji 679-2151, Russia.
Laboratory of Protein Physics, Institute of Protein Research RAS, Pushchino 142290, Russia.


The nature of renal amyloidosis involving Bence-Jones proteins in multiple myeloma is still unclear. The development of amyloidosis in neurodegenerative diseases is often associated with a high content of asparagine and glutamine residues in proteins forming amyloid deposits. To estimate the influence of Asn and Gln residues on the aggregation of Bence-Jones protein BIF, we obtained recombinant BIF and its mutants with the substitution of Tyr187→Asn (Y187N) in α-helix of CL domain, Lys170→Asn (K170N) and Ser157→Gln (S157Q) in CL domain loops, Arg109→Asn in VL-CL linker (R109N) and Asp29→Gln in VL domain loop (D29Q). The morphology of protein aggregates was studied at pH corresponding to the conditions in bloodstream (pH 7.2), distal (pH 6.5) and proximal renal tubules (pH 4.5) by atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS). The Lys170→Asn replacement almost completely inhibits amyloidogenic activity. The Y187N forms fibril-like aggregates at all pH values. The Arg109→Asn replacement resulted in formation of fibril-like structures at pH 7.2 and 6.5 while the substitutions by Gln provoked formation of those structures only at pH 7.2. Therefore, the amyloidogenic properties are highly dependent on the location of Asn or Gln.


Bence-Jones proteins; aggregation; atomic force microscopy; myeloma

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