Title

Synthesis of myristic acid analogs: Studying the substrate specificity of istoylCoA:protein N-myristoyltransferase, characterizing the enzyme's binding pocket, and treating viral as well as fungal infections

Date of Award

1993

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

George W. Gokel, Committee Chair

Abstract

Several viral and cellular proteins have recently been shown to be covalently modified during biosynthesis by N-myristoylation, the cotranslational attachment of a 14:0 fatty acid to an N-terminal glycine residue via an amide linkage. This cotranslational modification is catalyzed by the enzyme MyristoylCoA:protein N-myristoyltransferase (NMT). Protein N-myristoylation has attracted much attention due to the involvement of myristoylated proteins in the malignant transformation of cells and in the assembly of virus particles.Forty-six myristic acid analogs containing double bond, triple bond, aromatic ring, halogen, hydroxy, hydroxy on chiral carbon, oxygen, sulfur, nitro, azido, lactone and ketoxime and two $\sp{13}$C-labeled fatty acylCoAs have been successfully synthesized to study the substrate specificity of Saccharomyces cerevisiae myristoylCoA:protein N-myristoyltransferase (NMT), characterize the enzyme's acylCoA binding pocket, and treat viral as well as fungal infections.Surveying the bio-activities for these analogs tested as potential substrates for NMT using a coupled in vitro assay system indicated and suggested several things. First, NMT is remarkably selective for the fatty acid analogs having a 14 carbon chain length and it can tolerate both relatively nonpolar and polar functional groups, even protruding ones along the analog's backbone. It is also suspected that hydrogen bonding could be involved in NMT-substrate complexation. A polar or bulk substituent at positions C2 or C3 on the analog backbone may significantly disfavor its affinity for NMT. The hydrophobicity may be less important than chain length in determining substrate selectivity for NMT. Second, a testable model of the structure of a portion of the enzyme's acylCoA binding site can be further formulated (Fig. 2.23). Third, substrate capture by NMT may affect the efficiency and specificity of protein n-myristoylation in vivo. Finally, oxa-containing analogs which have altered physical-chemical properties relative to myristoylCoA may potentially inhibit both HIV-1 replication in vivo as well as the growth of organisms that cause opportunistic infections in patients with AIDS.

Keywords

Chemistry, Biochemistry

Link to Full Text

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