Full sequences of the constructs:

Human CTSA: MKFLVNVALVFMVVYISYIYADRHHHHHHGSAPDQDEIQRLPGLAKQPSFRQYSGYLKGSGSKHLHYWFVESQKDPENSPVVLWLNGGPGCSSLDGLLTEHGPFLVQPDGVTLEYNPYSWNLIANVLYLESPAGVGFSYSDDKFYATNDTEVAQSNFEALQDFFRLFPEYKNNKLFLTGESYAGIYIPTLAVLVMQDPSMNLQGLAVGNGLSSYEQNDNSLVYFAYYHGLLGNRLWSSLQTHCCSQNKCNFYDNKDLECVTNLQEVARIVGNSGLNIYNLYAPCAGGVPSHFRYEKDTVVVQDLGNIFTRLPLKRMWHQALLRSGDKVRMDPPCTNTTAASTYLNNPYVRKALNIPEQLPQWDMCNFLVNLQYRRLYRSMNSQYLKLLSSQKYQILLYNGDVDMACNFMGDEWFVDSLNQKMEVQRRPWLVKYGDSGEQIAGFVKEFSHIAFLTIKGAGHMVPTDKPLAAFTMFSRFLNKQPY

Mouse CTSA: MKFLVNVALVFMVVYISYIYADRHHHHHHGSAPDQDEIDALPGLAKQPSFRQYSGYLRASDSKHFHYWFVESQNDPKNSPVVLWLNGGPGCSSLDGLLTEHGPFLIQPDGVTLEYNPYAWNLIANVLYIESPAGVGFSYSDDKMYVTNDTEVAENNYEALKDFFRLFPEYKDNKLFLTGESYAGIYIPTLAVLVMQDPSMNLQGLAVGNGLASYEQNDNSLVYFAYYHGLLGNRLWTSLQTHCCAQNKCNFYDNKDPECVNNLLEVSRIVGKSGLNIYNLYAPCAGGVPGRHRYEDTLVVQDFGNIFTRLPLKRRFPEALMRSGDKVRLDPPCTNTTAPSNYLNNPYVRKALHIPESLPRWDMCNFLVNLQYRRLYQSMNSQYLKLLSSQKYQILLYNGDVDMACNFMGDEWFVDSLNQKMEVQRRPWLVDYGESGEQVAGFVKECSHITFLTIKGAGHMVPTDKPRAAFTMFSRFLNKEPY

Human GLB1: MKFLVNVALVFMVVYISYIYADRHHHHHHGSATQRMFEIDYSRDSFLKDGQPFRYISGSIHYSRVPRFYWKDRLLKMKMAGLNAIQTYVPWNFHEPWPGQYQFSEDHDVEYFLRLAHELGLLVILRPGPYICAEWEMGGLPAWLLEKESILLRSSDPDYLAAVDKWLGVLLPKMKPLLYQNGGPVITVQVENEYGSYFACDFDYLRFLQKRFRHHLGDDVVLFTTDGAHKTFLKCGALQGLYTTVDFGTGSNITDAFLSQRKCEPKGPLINSEFYTGWLDHWGQPHSTIKTEAVASSLYDILARGASVNLYMFIGGTNFAYWNGANSPYAAQPTSYDYDAPLSEAGDLTEKYFALRNIIQKFEKVPEGPIPPSTPKFAYGKVTLEKLKTVGAALDILCPSGPIKSLYPLTFIQVKQHYGFVLYRTTLPQDCSNPAPLSSPLNGVHDRAYVAVDGIPQGVLERNNVITLNITGKAGATLDLLVENMGRVNYGAYINDFKGLVSNLTLSSNILTDWTIFPLDTEDAVRSHLGGWGHRDGGHHDEAWAHNSSNYTLPAFYMGNFSIPSGIPDLPQDTFIQFPGWTKGQVWINGFNLGRYWPARGPQLTLFVPQHILMTSAPNTITVLELEWAPCSSDDPELCAVTFVDRPVIGSSVTYDHPSKPVEKRLMPPPPQKNKDSWLDHV

Mouse GLB1: MKFLVNVALVFMVVYISYIYADRHHHHHHGSVTQRTFKLDYSRDRFLKDGQPFRYISGSIHYFRIPRFYWEDRLLKMKMAGLNAIQMYVPWNFHEPQPGQYEFSGDRDVEHFIQLAHELGLLVILRPGPYICAEWDMGGLPAWLLEKQSIVLRSSDPDYLVAVDKWLAVLLPKMKPLLYQNGGPIITVQVENEYGSYFACDYDYLRFLVHRFRYHLGNDVILFTTDGASEKMLKCGTLQDLYATVDFGTGNNITQAFLVQRKFEPKGPLINSEFYTGWLDHWGKPHSTVKTKTLATSLYNLLARGANVNLYMFIGGTNFAYWNGANTPYEPQPTSYDYDAPLSEAGDLTKKYFALREVIQMFKEVPEGPIPPSTPKFAYGKVALRKFKTVAEALGILCPNGPVKSLYPLTFTQVKQYFGYVLYRTTLPQDCSNPKPIFSSPFNGVRDRAYVSVDGVPQGILDRNLMTALNIQGKAGATLDILVENMGRVNYGRFINDFKGLISNMTINSTVLTNWTVFPLDTEAMVRNHLWGREASDGGHLDGRSTSNSSDLILPTFYVGNFSIPSGIPDLPQDTFIQFPGWSKGQVWINGFNLGRYWPTMGPQKTLFVPRNILTTSAPNNITVLELEFAPCSEGTPELCTVEFVDTPVIS

Each protein was cloned into a modified pfastbac plasmid, downstream of a polyhedrin promoter. Recombinant bacmids were generated and transfected into Sf9 cells to establish recombinant baculovirus stocks.

For protein expressions, Sf9 cells were grown at 27 °C in I-MAX medium (Wisent Bio Products, 301-045-CL) with penicillin-streptomycin (Wisent Bio Products, 450-201-EL). The baculovirus stock was added at 3.5 % by volume and expression was carried out for 68 hours. The cultures were clarified by centrifugation. The supernatant was incubated with 1 % by volume of HisPur Ni-NTA resin (Thermo Scientific, 88222) at 22 °C with shaking for 1 hour. The resin was pelleted by centrifugation at 1k g for 5 minutes, and washed with 20 volumes of wash buffer (25 mM Tris-HCl pH 7.5 (at 22 °C), 500 mM NaCl, 10 mM imidazole) by gravity flow. The protein was eluted with 3 volumes of elution buffer (wash buffer supplemented with 250 mM imidazole) and concentrated to 0.5 mL (or up to 20 mg/mL) with 30k Amicon Ultra-15 centrifugal filters (Millipore Sigma, UFC903024) at 4 °C. The sample was loaded on a Superdex 200 Increase 10/300 size-exclusion chromatography column (Cytivia, 28990944) in buffer (10 mM Tris-HCl pH 8.1 (at 4 °C), 100 mM NaCl). The fractions containing the protein were concentrated to 10 mg/mL and flash-frozen. Typical final yields were between 2 to 6 mg per L of culture for GLB1, and 21 to 38 mg per L for CTSA.