The invention provides compositions and methods for covalent attachment of polymer and lipid carriers to therapeutic proteins to form carrier-protein conjugates having linkers between the carrier and protein portions of the conjugates. The linkers are selected to minimize steric effects. The linkers reduce the shielding effect of the carrier on the therapeutic protein and also allow better access for enzymatic or chemical cleavage of the carbamate bond. The linkers attach to the therapeutic protein via a carbamate bond and are either directly adjacent to the carbamate bond or are separated by a single carbon having a nitrogen side chain. Such linkers are solely comprised of carbon, sulfur and hydrogen and are between four and ten atoms (either C or S) in length.