N-terminal amino acid sequencing of EDP208 conjugative pili

EDP208 conjugative pili contain a single polypeptide subunit of 11,500 daltons with a blocked N-terminus. This N-terminal blocking moiety was identified as an N-acetyl group by 1H nuclear magnetic resonance analysis of an N-terminal tripeptide isolated from pronase digests of EDP208 pilin. Limited acid hydrolysis of the tripeptide allowed its sequence to be determined as acetyl-NH-Thr-Asp-Leu. Trypsin digestion of EDP208 pilin resulted in the quantitative release of a fragment containing 12 residues from the N-terminus of the protein. The sequence of this dodecapeptide was determined to be acetyl-NH-Thr-Asp-Leu-Leu-Ala-Gly-Gly-Lys-Asp-Val-Asp-Lys.