Comparative Analysis of Aggregation of Thermus thermophilus Ribosomal Protein bS1 and Its Stable Fragment

Functionally important multidomain bacterial protein bS1 is the largest ribosomal protein of subunit 30S. It interacts with both mRNA and proteins and is prone to aggregation, although this process has not been studied in detail. Here, we obtained bacterial strains overproducing ribosomal bS1 protein from Thermus thermophilus and its stable fragment bS1(49) and purified these proteins. Using fluorescence spectroscopy, dynamic light scattering, and high-performance liquid chromatography combined with mass spectrometric analysis of products of protein limited proteolysis, we demonstrated that disordered regions at the N- and C-termini of bS1 can play a key role in the aggregation of this protein. The truncated fragment bS1(49) was less prone to aggregation compared to the full-size bS1. The revealed properties of the studied proteins can be used to obtain protein crystals for elucidating the structure of the bS1 stable fragment.