Sequential pH-driven dimerization and stabilization of the N-terminal domain enables rapid spider silk formation

• The mechanisms controlling the conversion of spider silk proteins into insoluble fibres, which happens in a fraction of a second and in a defined region of the silk glands, are still unresolved. The N-terminal domain changes conformation and forms a homodimer when pH is lowered from 7 to 6; however, the molecular details still remain to be determined. Here we investigate site-directed mutants of the N-terminal domain from Euprosthenops australis major ampullate spidroin 1 and find that the charged residues D40, R60 and K65 mediate intersubunit electrostatic interactions. Protonation of E79 and E119 is required for structural conversions of the subunits into a dimer conformation, and subsequent protonation of E84 around pH 5.7 leads to the formation of a fully stable dimer. These residues are highly conserved, indicating that the now proposed three-step mechanism prevents premature aggregation of spidroins and enables fast formation of spider silk fibres in general.

Ämnesord

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

NATURVETENSKAP  -- Biologi -- Strukturbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Structural Biology (hsv//eng)

Nyckelord

animal; biosynthesis; chemistry; dimerization; genetics; metabolism; nuclear magnetic resonance spectroscopy; pH; spectrofluorometry; spider; static electricity

Biological Physics

Biologisk fysik

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