Table 1.

Masses of Cys-containing peptides for alkylated, de-N-glycosylated, tryptic digests of NL3-639 proteins a

Observed masses
Disulfide linkages NL3-639 peptides Calculated massesb Wild type R471C
C106-C141 D98-R195c 6628.56d 6627.69 6628.11
C293e I282-R309 2974.42 2974.43 2974.40
C340-C351 V338-R353 1749.81 1749.78 1749.76
C510-C544 Y497-K548c 5877.69 5877.85 5876.64f
  • a Seventy-three percent of NL3-639 amino acid sequence was accounted for in acquired mass spectra. The small tryptic peptide (471-K472 of the R471C mutant is not observed being below the limit of mass detection.

  • b Masses are calculated from amino acid sequence (monoisotopic masses are given below 2000 Da, average masses above 2000 Da).

  • c Native Asn is converted to Asp by PNGase F treatment.

  • d Numbering includes an alternative splice sequence of 40 aa not found in NL3.

  • e Free Cys293 is alkylated by iodoacetamide treatment of NL3 proteins.

  • f Weak ionization signal compared with wild type.