Open AccessFluorescence Anisotropy Decays and Microscale-Volume Viscometry Reveal the Compaction of Ribosome-Bound Nascent Proteins
Author(s) -
Rachel Hutchinson,
Xi Chen,
Ningkun Zhou,
Silvia Cavagnero
Publication year - 2021
Publication title -
the journal of physical chemistry. b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 392
eISSN - 1520-6106
pISSN - 1520-5207
DOI - 10.1021/acs.jpcb.1c04473
Subject(s) - microscale chemistry , folding (dsp implementation) , ribosome , viscometer , fluorescence , macromolecule , chemistry , crystallography , fluorescence anisotropy , anisotropy , fluorophore , protein folding , chemical physics , biophysics , physics , biochemistry , rna , biology , thermodynamics , viscosity , optics , mathematics education , mathematics , electrical engineering , engineering , gene
This work introduces a technology that combines fluorescence anisotropy decay with microscale-volume viscometry to investigate the compaction and dynamics of ribosome-bound nascent proteins. Protein folding in the cell, especially when nascent chains emerge from the ribosomal tunnel, is poorly understood. Previous investigations based on fluorescence anisotropy decay determined that a portion of the ribosome-bound nascent protein apomyoglobin (apoMb) forms a compact structure. This work, however, could not assess the size of the compact region. The combination of fluorescence anisotropy with microscale-volume viscometry, presented here, enables identifying the size of compact nascent-chain subdomains using a single fluorophore label. Our results demonstrate that the compact region of nascent apoMb contains 57-83 amino acids and lacks residues corresponding to the two native C-terminal helices. These amino acids are necessary for fully burying the nonpolar residues in the native structure, yet they are not available for folding before ribosome release. Therefore, apoMb requires a significant degree of post-translational folding for the generation of its native structure. In summary, the combination of fluorescence anisotropy decay and microscale-volume viscometry is a powerful approach to determine the size of independently tumbling compact regions of biomolecules. This technology is of general applicability to compact macromolecules linked to larger frameworks.