Author response image 1. Mass spectrometry analysis of the long uromodulin isoform released by MDCK cells.
(A) Mass spectrometry sequence coverage (42%) of Asp-N-digested human uromodulin (long isoform) from the medium of stably expressing MDCK cells. The analysis was carried out as described in the Methods section of the manuscript. The long isoform was separated in 2D electrophoresis. Matching peptides are shown in red, while the C- terminal peptide is shown in blue. This peptide ends at A611, a distal C-terminal relative to the one identified for the short isoform (F587) that is identical to the one reported for human urinary uromodulin (Santambrogio et al., 2008). (B) Representative tandem mass-spectrometry (MS/MS) spectrum confirming the identity of the 594DQSRVLNLGPITRKGVQA611 C-terminal peptide of the long uromodulin isoform released by MDCK cells and table of fragmented ions.