Appearance of "b-Like" Circular Dichroism Spectra on Protein Aggregation That Is not Accompanied by Transition to b-Structure

• Published in: Biochemistry (Moscow) Vol. 66; no. 12; pp. 1378 - 1380
• Main Authors: Arutyunyan, AM, Rafikova, E R, Drachev, V A, Dobrov, EN
• Format: Journal Article
• Language: English
• Published: 01.12.2001
• Subjects: Tobacco mosaic virus
• ISSN: 0006-2979; 1608-3040
• DOI: 10.1023/A:1013337930104

CD spectra in the 200 to 250 nm spectral region for small ordered aggregates (trimers-pentamers) of tobacco mosaic virus (TMV) coat protein (CP) and for long virus-like helical aggregates of TMV CP were compared. It was found that small (4S) TMV CP aggregates have a CD spectrum typical of a protein with high a-helix content, which agrees well with results of X-ray diffraction studies. But in the long helical aggregates (and in the TMV virions) TMV CP gives "b-like" CD spectra similar to those of many other aggregated proteins. From X-ray diffraction data, it is well known that TMV CP subunits do not change their secondary or tertiary structure on assembly into virions or the helical repolymerized protein. Thus, the change in the shape of 200 to 250 nm CD spectra cannot be employed as the sole criterion of the conversion of a protein to b-structure in the course of aggregation.