Updated project metadata. Budding yeast Tsr1 is an essential ribosome biogenesis factor that is required for cytoplasmic steps in 40S subunit maturation. S. cerevisiae Tsr1 was expressed as an N-terminal GST fusion protein in E. coli. A mutant Tsr1ΔNΔloop was generated in which residues 410 to 476 of Tsr1 were replaced with a short glycine and serine rich sequence; in addition, the N-ternimal 45 amino acid residues were replaced by five amino acid residues “GPDSD”. Tsr1ΔNΔloop allowed for generating native crystals that diffracted to 3.6 Å. Here we characterize both wild type Tsr1 and Tsr1ΔNΔloop using cross-linking/mass spectrometry.