Biomolecular Mass Spectrometry: Applications to Proteins and Peptides - Molecules: Nucleation, Aggregation and Crystallization - page 67

100

810 208 +/- 963 Da

1 516 052 +/- 1986 Da

2 325 463 +/- 2003 Da

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Fig. 6. (a) MS of intact Thermus thermophilus ribosomes is accompanied by release of
some individual protein components. An unknown component of ∼96 kDa (red arrow)
not corresponding to any known proteins or subcomplexes of the ribosomes was later
determined to be a non-canonical trimer of the L7/L12 stalk proteins. (b) Tandem MS of
50S ribosomal subunit allows detection of stalk proteins (inset) without loss of the struc-
tural information as to their origin (i.e. bound to the 50S as opposed to free proteins in
solution). Further analysis of the data indicated the presence of phosphorylated L7/L12
proteins. Models are based on the Protein Data Bank structures 1GIX and 1GIY.