The skeletal muscle type 1 ryanodine receptor (RyR1; 5,037 residues) forms a homo-tetrameric Ca²⁺-release channel in the sarcoplasmic reticulum (SR), mediates excitation-contraction coupling in response to an orthograde signal from the dihydropyridine receptor (DHPR) in the plasma membrane, and retrogradely enhances L-type Ca²⁺ current via the DHPR. The RyR1 C-terminus contains the Ca²⁺ channel pore across the SR membrane and is believed to be important for inter-subunit interactions, whereas the bulk (~85%) of the protein (the so-called foot) bridges the junctional, myoplasmic gap between the SR and plasma membranes. Here, we examined the ability of the foot domain (residues 1-4,300; RyR1_1:4300) to target junctionally by expression of YFP-RyR1_1:4300. In dysgenic (α_1S-null) myotubes which lack DHPRs, YFP-RyR1_1:4300 was diffusely distributed and, on the basis of FRAP, freely mobile within the cytoplasm with a diffusion coefficient of 2.17x10^-8 cm²/sec, compatible with YFP-RyR1_1:4300 existing as a tetramer. However, after expression in dyspedic (RyR1 null) myotubes (which have DHPRs), YFP-RyR1_1:4300 was often immobile within fluorescent foci near the myotube surface and partially co-localized with the DHPR. Strikingly, YFP-RyR1_1:4300 was able to retrogradely enhance peak Ca²⁺ current in dyspedic myotubes from 1.6 pA/pF (control) to 6.7 pA/pF, similar to that after expression of full-length RyR1 (7.4 pA/pF). Immunoblotting in combination with chemical cross-linking revealed that YFP-RyR1_1:4300, much like wt full-length RyR1, in 4-15% SDS gradient gels migrates as single band of high apparent MW, consistent with it's being a tetramer.