Myristylation is required for intracellular transport but not for assembly of D-type retrovirus capsids

Abstract

The role of myristylation, a fatty acid modification of nascent polypeptides, in the assembly and intracellular transport of D-type retroviral capsids was investigated through the use of oligonucleotide-directed mutagenesis. Myristic acid is normally esterified through an amide linkage to a glycine residue at the amino terminus of the Mason-Pfizer monkey virus gag gene products. Mutant pA-1, which has a codon for valine substituted for that of the normally myristylated glycine, is completely noninfectious. While the mutant gag polyprotein precursors are synthesized at normal levels, they are not myristylated and are not cleaved to the mature virion proteins. No extracellular virus particles are released from mutant pA-1-infected cells, but intracytoplasmic A-type particles (capsids) accumulate in the cytoplasm. Since none of the intracellular capsids can be found associated with the plasma membrane, these results strongly suggest that myristylation is a critical signal for intracytoplasmic transport of completed viral capsids to their normal site of budding and release.

Molecular aspects of the interaction between Mason—Pfizer monkey virus matrix protein and artificial phospholipid membrane

“…Although several differences occur between free and bound MA, all arginine residues were modified in both states (Table I). Modified residues R10 and R58 were detected in the peptide [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] and [58][59][60][61][62][63][64][65][66][67][68][69][70][71][72][73][74] in the both states. Modification of arginine in the position 22 was detected in the free protein within the peptide [21][22][23][24][25].…”

“…Analysis of the free MA showed that all lysine residues were accessible to the NHS modification (Table II). Modification of lysines in the fragments [11][12][13][14][15][16][17][18][19][20], [11][12][13][14][15][16][17][18][19][20][21][22], [28][29][30][31][32][33][34][35][36][37][38][39], , [75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94], and [93-111] led to the d...…”

“…[6][7][8][9] Type D retroviruses assemble their spherical protein shell (immature viral particle) from the structural polyproteins mediated by the N-terminal domain of Gag, the matrix protein. [12][13][14][15] The matrix protein is myristoylated on its N-terminus and this modification is indispensable for the virus trafficking and binding to the membrane. 13 Furthermore, the important role of the basic residues of M-PMV matrix protein was revealed by mutation studies.…”

“…[12][13][14][15] The matrix protein is myristoylated on its N-terminus and this modification is indispensable for the virus trafficking and binding to the membrane. 13 Furthermore, the important role of the basic residues of M-PMV matrix protein was revealed by mutation studies. The mutations of residues K16, K20, K33, and K39 affected the specificity or effectivity of immature capsids budding, whereas mutants R10A, R22A, K25A, and K27A were defective in the transport of immature capsids to the plasma membrane.…”

Variable Sensitivity to Substitutions in the N-Terminal Heptad Repeat of Mason-Pfizer Monkey Virus Transmembrane Protein

“…The other set was then chased in complete DMEM for an additional 4 h prior to lysis of the cells. Using a goat anti-M-PMV antibody, viral proteins in the cell lysates were immunoprecipitated and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) as previously described (39).…”