computer analysis of known ness found the most common spacing of the hydrophobic residues to be lxxxlxxlxl, where "l" is a hydrophobic residue (often leucine) and "x" is any other amino acid; the spacing of these hydrophobic residues may be explained by examination of known structures that contain an nes, as the critical residues usually lie in the same face of adjacent secondary structures within a protein, which allows them to interact with the exportin. ribonucleic acid (rna) is composed of nucleotides, and thus, lacks the nuclear export signal to move out of the nucleus. as a result, most forms of rna will bind to a protein molecule to form a ribonucleoprotein complex to be exported from the nucleus.