Fig. 2

Investigation of TEX101 isoforms in spermatozoa and seminal plasma (SP) using selected reaction monitoring (SRM). Semen samples from men with a high sperm count (≥7 million/mL) and unexplained infertility and oligospermia (N = 17, see Additional file 4: Table S3) were centrifuged to separate spermatozoa from SP, which were then analyzed by SRM. Peptide AGTETAILATK common for both isoforms was used to quantify total TEX101, while unique peptide QIQTSSSQTSPEEAMGTPR was used to detect the presumed intracellular TEX101 isoform Q9BY14-2. Corresponding heavy isotope-labeled peptides were used as internal standards. Intracellular isoform Q9BY14-2 was not detected in either spermatozoa or SP, so total TEX101 was assumed to be a 249 amino acid (aa) extracellular membrane isoform Q9BY14-1. The checkmark indicates detection and X the absence of the peptides shown