5v7f
T4 lysozyme Y18Ymi
Structural highlights
FunctionENLYS_BPT4 Endolysin with lysozyme activity that degrades host peptidoglycans and participates with the holin and spanin proteins in the sequential events which lead to the programmed host cell lysis releasing the mature viral particles. Once the holin has permeabilized the host cell membrane, the endolysin can reach the periplasm and break down the peptidoglycan layer.[1] Publication Abstract from PubMedThe construction of more stable proteins is important in biomolecular engineering, particularly in the design of biologics-based therapeutics. We show here that replacing the tyrosine at position 18 (Y18) of T4 lysozyme with the unnatural amino acid m-chlorotyrosine ( (mCl)Y) increases both the thermal stability (increasing the melting temperature by approximately 1 degrees C and the melting enthalpy by 3 kcal/mol) and the enzymatic activity at elevated temperatures (15% higher than that of the parent enzyme at 40 degrees C) of this classic enzyme. The chlorine of (mCl)Y forms a halogen bond (XB) to the carbonyl oxygen of the peptide bond at glycine 28 (G28) in a tight loop near the active site. In this case, the XB potential of the typically weak XB donor Cl is shown from quantum chemical calculations to be significantly enhanced by polarization via an intramolecular hydrogen bond (HB) from the adjacent hydroxyl substituent of the tyrosyl side chain, resulting in a distinctive synergistic HB-enhanced XB (or HeX-B for short) interaction. The larger halogens (bromine and iodine) are not well accommodated within this same loop and, consequently, do not exhibit the effects on protein stability or function associated with the HeX-B interaction. Thus, we have for the first time demonstrated that an XB can be engineered to stabilize and increase the activity of an enzyme, with the increased stabilizing potential of the HeX-B further extending the application of halogenated amino acids in the design of more stable protein therapeutics. Increasing Enzyme Stability and Activity through Hydrogen Bond-Enhanced Halogen Bonds.,Carlsson AC, Scholfield MR, Rowe RK, Ford MC, Alexander AT, Mehl RA, Ho PS Biochemistry. 2018 Jul 3. doi: 10.1021/acs.biochem.8b00603. PMID:29921126[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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