title: Segmental flexibility in Escherichia coli ribosomal protein S1 as studied by fluorescence polarization.
abstract: Ribosomal protein S1 covalently reacts with approximately one equivalent of iodoacetylethylenediamine (1,5-napthol sulfonate (IAEDANS) or iodoacetylaminofluorescein (IAAF). The product AEDANS-S1 can bind to 30S ribosomal subunits lacking S1 as shown by polyacrylamide-agarose gel electrophoresis AEDANS-S1 and AAF-S1 when added back to S1-depleted 30S subunits modulate poly(U)-dependent polyphenylalanine synthesis in the presence of IF3 in a very similar way to unmodified S1. AEDANS-S1 also stimulates RI7-dependent fMet-tRNA binding to 1.0M NH4C1 washed ribosomes whereas AAF-S1 does not. Both static and nanosecond fluorescence polarization techniques were used to study the rotational motions of AEDANS-S1. Several previous studies had indicated that S1 is a highly extended protein which can be modeled by a prolate ellipsoid with an axial ratio of 10 to 1. However, the rotational correlation time we find is about half that expected for such a particle. This suggests that S1 is a flexible protein with at least two domains that can rotate independently.
mesh_terms: D004926:Escherichia coli / Q000378:metabolism*; D007700:Kinetics; D011072:Poly U; D014176:Protein Biosynthesis; D011487:Protein Conformation; D012333:RNA, Messenger / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism; D012270:Ribosomes / Q000032:analysis; D013050:Spectrometry, Fluorescence
chemical_list: D012333:RNA, Messenger; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins; D011072:Poly U