Neurexophilin 1, Recombinant, Rat (NXPH1)

Neurexophilin-1 (NXPH-1) is one of at least four vertebrate neuropeptide-like secreted glycoproteins in the neurexophilin family (1, 2). The 29 kD, 271 amino acid (aa) NXPH-1 sequence contains a 22 aa signal peptide, a 94 aa propeptide that is cleaved at a basic motif, and a 115 aa mature protein that contains three potential N-glycosylation sites in the N-terminal portion and six conserved cysteines in the C-terminal portion (1). Mature rat NXPH-1 shares 99%, 99%, 99%, 96% and 84% aa identity with mouse, human, bovine, opossum and zebrafish NXPH-1, respectively. NXPH-1 is expressed selectively in subpopulations of neurons within the cerebral cortex, cerebellum and olfactory bulb that are thought likely to be inhibitory interneurons (2, 3). NXPH-3 is the neurexophilin most similar to NXPH-1, sharing 69% aa identity within the mature region. Expression of NXPH-1 and NXPH-3 does not appear to coincide, but both are tightly bound extracellular ligands of alpha-neurexins, synaptic transmembrane molecules that are essential for calcium-triggered neurotransmitter release (1, 4, 5). Genetic deletion of NXPH-1 and/or NXPH-3 produces no anatomical effect, although mice lacking NXPH-3 show defects in motor coordination (4, 6). Of the other known neurexophilins, NXPH-2 is not expressed in rodents, and NXPH-4 does not bind alpha-neurexins (1, 4). Source: Rat Neurexophilin-1 (Met 1-Gly 271), HHHHHH, A DNA sequence encoding rat neurexophilin-1 (Met 1-Gly 271, Accession # Q63366) was fused to a 6X histidine tag at the C-terminus. The protein was expressed in a mouse myeloma cell line, NS0. , Molecular Mass: Based on N-terminal sequencing, the recombinant rat neurexophilin-1 starts at Ala 22 and has a predicted molecular mass of 29.4 kD. A secondary sequence accounting for approximately 30% of the protein abundance begins at Arg 107. As a result of glycosylation the recombinant rat Neurexophilin-1 migrates at approximately 42-50 kD and 27-30 kD in SDS-PAGE under reducing conditions. Endotoxin Level: < 1.0 EU per 1 µg of protein as determined by the LAL method. , Activity: Measured in a competitive binding assay. When recombinant rat neurexin-1 alpha is coated at 1ug/ml (100 µL/well), rrNXPH-1 inhibits 50% binding of rrNXPH-1 biotin (1ug/ml) at the concentration range of 1-3ug/ml. Reconstitution: It is recommended that sterile PBS be added to the vial to prepare a working stock solution of no less than 100ug/ml. The carrier-free protein should be used immediately upon reconstitution to avoid losses in activity due to non-specific binding to the inside surface of the vial. For long term storage as a dilute solution, a carrier protein (e.g. 0.1% HSA or BSA) should be added to the vial. , Storage and Stability: Lyophilized samples are stable for up to twelve months at -20°C. Upon reconstitution, this protein, in the presence of a carrier protein, can be stored under sterile conditions at 2°-8° C for one month or at -20°C in a manual defrost freezer for three months without detectable loss of activity. Avoid repeated freeze-thaw cycles.