Elastase amino acid sequence determination

We were also able to use FAB mass spectrometry to determine the amino acid sequence around the active site serine in the acyl transference domain of rabbit mammary fatty acid synthase.6 The synthase was labelled in the acyl transferase domain(s) by the formation of O-ester intermediates after incubation with [" " C]-acetyl- or malonyl-CoA (Fig. 2A). The modified protein was then digested with elastase (Fig. 2B), and radioactive material isolated via successive purification steps on Sephadex G-50 and reverse phase HPLC. The isolated peptides were then sequenced by FAB MS. The data summarized in Table II established the sequences of both the acetyl and malonyl hexapeptides to be N-acyl-Ser-leu-Gly-Glu-Val-Ala. 

Fig. 8.9. Chemical reactivity of individual amino acid side chains in native elastase. The reagents used were [ C]acetic anhydride (A) [ " C]dimethyl sulfate ( ) and [ " C]iodoacetate ( ). The reference value for a totally accessible group was the chemical reactivity determined in the denatured and reduced form of the protein. The lower part of the figure indicates all the modified side chains along the sequence (from Ghelis, 1980).

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