Act-2 is a member of a family of small secreted proteins, many members of which have inflammatory or chemotactic activities. This family, whose members are now denoted as """"""""chemokines"""""""" can be divided into two subfamilies based on whether the first two of four conserved cysteines are adjacent (CC) or separated by one amino acid (CXC). Act-2 is a member of the CC subfamily, and is presumed to be the human homologue of macrophage inflammatory protein (MIP)-1beta. Act-2 is chemotactic for CD4(+) T lymphocytes. Synthesis and secretion of this cytokine are rapidly induced in T cells, B cells, and monocytes following stimulation with antigen or mitogen. During the past year, we reported that Act-2 protein has activity as a bone marrow stem cell inhibitor and can efficiently compete with murine MIP-1alpha for binding. In addition, Act-2 protein was produced in both bacterial and baculovirus expression systems and structural analysis of the protein is underway. After confirming quality of the recombinant Act-2 protein by one dimensional NMR, more than 10 mg each of unlabeled, (15)N-labeled, and (15)N plus (13)C doubly labeled Act-2 protein were produced analyzed by multidimensional NMR. Structural analysis is in progress. Crystals of Act-2 are also being made for use in Xray crystallography. Knowledge of the structure is vital to eventual drug agonist/antagonist development as well as being scientifically important since no structural information is yet available on any members of the CC subfamily.
