bcl-X Protein. bcl-X(L) Protein . bcl-X(S) Protein . bcl-Xa Protein . bcl-Xalpha Protein . bcl-Xb Protein . bcl-Xbeta Protein . bcl-Xlong Protein . bcl-Xshort Protein . bcl-x(beta) Protein . bcl2-Like 1 Protein . bcl2L1 Protein . bcl X Protein . bcl XL Protein . bcl XS Protein . bcl Xa Protein . bcl Xalpha Protein . bcl Xb Protein . bcl Xbeta Protein . bcl Xlong Protein . bcl Xshort Protein . bcl2 Like 1 Protein . bcl-XL Protein . bcl-XS Protein . A member of the bcl-2 protein family that plays a role in the regulation of APOPTOSIS and is a regulatory subunit for PROTEIN PHOSPHATASE 1. Two major isoforms of the protein exist due to ALTERNATIVE SPLICING of the BCL2L1 mRNA and are referred to as Bcl-XS and Bcl-XL. . 0.54