To prepare dough, dissolve yeast in warm water in a large bowl; let stand 5 minutes. Add 1/4 cup sugar, 1/2 cup sour cream, 2 tablespoons softened butter, salt, and egg, and beat with a mixer at medium speed until smooth. Lightly spoon flour into dry measuring cups; level with a knife. Add 2 cups flour to yeast mixture; beat until smooth. Add 1 cup flour to yeast mixture, stirring until a soft dough forms. Turn dough out onto a floured surface. Knead until smooth and elastic (about 10 minutes); add enough remaining flour, 1 tablespoon at a time, to prevent dough from sticking to hands (dough will feel sticky).
Place dough in a large bowl coated with cooking spray, turning to coat top. Cover and let rise in a warm place (85°), free from drafts, 1 hour and 15 minutes or until doubled in size. (Gently press two fingers into dough. If indentation remains, dough has risen enough.)
Punch dough down; cover and let rest 5 minutes. Divide dough in half. Working with 1 portion at a time (cover remaining dough to prevent drying), roll each portion of dough into a 12-inch circle on a floured surface. Brush surface of each circle with 1 tablespoon melted butter. Combine 3/4 cup sugar and rind. Sprinkle half of sugar mixture over each circle. Cut each circle into 12 wedges. Roll up each wedge tightly, beginning at wide end. Place rolls, point sides down, in a 13 x 9-inch baking pan coated with cooking spray. Cover and let rise 25 minutes or until doubled in size.
Preheat oven to 350°.
Uncover dough. Bake at 350º for 25 minutes or until golden brown.
While rolls bake, prepare the glaze. Combine 3/4 cup sugar, 1/4 cup butter, and orange juice in a small saucepan; bring to a boil over medium-high heat. Cook 3 minutes or until sugar dissolves, stirring occasionally. Remove from heat; cool slightly. Stir in 1/2 cup sour cream. Drizzle glaze over warm rolls; let stand 20 minutes before serving.