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Biochem Biophys Res Commun. 2014 Jan 10;443(2):495-9. doi: 10.1016/j.bbrc.2013.11.123. Epub 2013 Dec 7.

The N-terminal strand modulates immunoglobulin light chain fibrillogenesis.

Author information

1
Instituto Nacional de Medicina Genómica, Periférico Sur No. 4809, Col. Arenal Tepepan, Delegación Tlalpan, México, D.F. C.P. 14610, Mexico. Electronic address: ldelpozo@inmegen.gob.mx.
2
Departments of Radiology and Medicine, The University of Tennessee Medical Center, 1924 Alcoa Highway, Knoxville, TN, USA.
3
Instituto Nacional de Medicina Genómica, Periférico Sur No. 4809, Col. Arenal Tepepan, Delegación Tlalpan, México, D.F. C.P. 14610, Mexico.
4
Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad #2001, Col. Chamilpa Cuernavaca, Morelos C.P. 62210, Mexico.
5
Centro de Desarrollo de Productos Bióticos, Instituto Politécnico Nacional, Calle CEPROBI No. 8, Col. San Isidro, Yautepec, Morelos C.P. 62731, Mexico.
6
Unidad de Genómica de Poblaciones Aplicada a la Salud, Facultad de Química, UNAM-Instituto Nacional de Medicina Genómica (INMEGEN), Periférico Sur No. 4809, Col. Arenal Tepepan, Delegación Tlalpan México, D.F. C.P. 14610, Mexico.
7
Laboratorio de Fisicoquímica e Ingeniería de Proteínas, Departamento de Bioquímica, Facultad de Medicina, Universidad Nacional Autónoma de México, Circuito Interior, Ciudad Universitaria, Av. Universidad 3000, México, D.F. C.P. 04510, Mexico.

Abstract

It has been suggested that the N-terminal strand of the light chain variable domain (V(L)) protects the molecule from aggregation by hindering spurious intermolecular contacts. We evaluated the impact of mutations in the N-terminal strand on the thermodynamic stability and kinetic of fibrillogenesis of the V(L) protein 6aJL2. Mutations in this strand destabilized the protein in a position-dependent manner, accelerating the fibrillogenesis by shortening the lag time; an effect that correlated with the extent of destabilization. In contrast, the effect on the kinetics of fibril elongation, as assessed in seeding experiments was of different nature, as it was not directly dependant on the degree of destabilization. This finding suggests different factors drive the nucleation-dependent and elongation phases of light chain fibrillogenesis. Finally, taking advantage of the dependence of the Trp fluorescence upon environment, four single Trp substitutions were made in the N-terminal strand, and changes in solvent exposure during aggregation were evaluated by acrylamide-quenching. The results suggest that the N-terminal strand is buried in the fibrillar state of 6aJL2 protein. This finding suggest a possible explanation for the modulating effect exerted by the mutations in this strand on the aggregation behavior of 6aJL2 protein.

KEYWORDS:

Aggregation; Amyloid; Folding thermodynamics; Light chain; Misfolding

PMID:
24321098
DOI:
10.1016/j.bbrc.2013.11.123
[Indexed for MEDLINE]

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