The Role of Poly-(R)-3-Hydroxybutyrate in Ribosomal Structure and Function
Crumbaugh, Amanda J.
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Current ribosomal research has primarily focused on understanding structural details at the molecular level in order to obtain a complete understanding of ribosomal function. One poorly understood structural component is poly-(R)-3-hydroxybutyrate (PHB), a polymer derived from acetate that is found attached to many different proteins in all parts of the cell. In this study, ribosomal proteins (r-proteins) from Escherlchia coli were isolated by differential centrifugation followed by gel electrophoresis, and analyzed by immunoassay and Edman degradation sequencing to identify those modified by PHB. Three r-proteins were already known to contain the polymer, and two more proteins from the large subunit (L) were also found to contain it - LS and L13. This structural information allows formation of a hypothesis about the role PHB could play in the translation process. L5 is a 5S RNA binding protein, and PHB is known to solvate polyphosphates. Here, it may facilitate proper binding and orientation of the 5S RNA molecule. The PHB attached to L13 could provide structural support to the 23S RNA, or may also interact with incoming mRNA molecules and aid their entry into the hydrophobic interior of the ribosome. Both proteins have important functions within the ribosome, and the polyester covalently bound to them may also constitute an essential part of protein production that has not yet been recognized.