Drosophila ACT88F indirect flight muscle-specific actin is not N-terminally acetylated: A mutation in N-terminal processing affects actin function

TY - JOUR

T1 - Drosophila ACT88F indirect flight muscle-specific actin is not N-terminally acetylated: A mutation in N-terminal processing affects actin function

AU - Schmitz, S

AU - Clayton, J

AU - Nongthomba, U

AU - Prinz, H

AU - Veigel, C

AU - Geeves, M

AU - Sparrow, J

PY - 2000/2/4

Y1 - 2000/2/4

N2 - Many eukaryotic proteins are co and post-translationally modified at their N termini by removal of one or two amino acid residues and N-infinity-acetylation. Actins show two different forms of N-terminal processing dependent on their N-terminal sequence. Ln class II actins, which include muscle actins, the common primary sequence of Met-Cys-Asp-actin is processed to acetyl-Asp-actin. The functional significance of this in vivo is unknown. We have studied the indirect flight muscle-specific actin, ACT88F, of Drosophila melanogaster. Our results show that ACT88F is N-terminally processed in vivo as a class II actin by removal of the first two amino acid residues (Met and Cys), but that uniquely the N terminus is not acetylated. Ln addition we show that ACT88F is methylated, probably at His73.Flies carrying the mod(-) mutation fail to complete post-translational processing of ACT88F. We propose that the mon gene product is normally responsible for removing N-acetyl-cysteine from actin. The biological significance of this process is demonstrated by observations that retention of the N-acetyl-cysteine in ACT88F affects the flight muscle function of mod(-) flies. This suggests that the extreme N terminus affects actomyosin interactions in vivo, a proposal we have examined by in vitro motility assays of ACT88F F-actin from mod(-) flies. The mod(-) actin only moves in the presence of methylcellulose, a viscosity-enhancing agent, where it moves at velocities slightly, but significantly, reduced compared to wild-type. These data confirm that N-acetyl-cysteine at the N terminus affects actomyosin interactions, probably by reducing formation of the initial actomyosin collision complex, a process known to involve the actin N terminus. (C) 2000 Academic Press.

AB - Many eukaryotic proteins are co and post-translationally modified at their N termini by removal of one or two amino acid residues and N-infinity-acetylation. Actins show two different forms of N-terminal processing dependent on their N-terminal sequence. Ln class II actins, which include muscle actins, the common primary sequence of Met-Cys-Asp-actin is processed to acetyl-Asp-actin. The functional significance of this in vivo is unknown. We have studied the indirect flight muscle-specific actin, ACT88F, of Drosophila melanogaster. Our results show that ACT88F is N-terminally processed in vivo as a class II actin by removal of the first two amino acid residues (Met and Cys), but that uniquely the N terminus is not acetylated. Ln addition we show that ACT88F is methylated, probably at His73.Flies carrying the mod(-) mutation fail to complete post-translational processing of ACT88F. We propose that the mon gene product is normally responsible for removing N-acetyl-cysteine from actin. The biological significance of this process is demonstrated by observations that retention of the N-acetyl-cysteine in ACT88F affects the flight muscle function of mod(-) flies. This suggests that the extreme N terminus affects actomyosin interactions in vivo, a proposal we have examined by in vitro motility assays of ACT88F F-actin from mod(-) flies. The mod(-) actin only moves in the presence of methylcellulose, a viscosity-enhancing agent, where it moves at velocities slightly, but significantly, reduced compared to wild-type. These data confirm that N-acetyl-cysteine at the N terminus affects actomyosin interactions, probably by reducing formation of the initial actomyosin collision complex, a process known to involve the actin N terminus. (C) 2000 Academic Press.

KW - Drosophila

KW - actin

KW - N terminus

KW - processing

KW - mutation

KW - AMINO-ACID SEQUENCE

KW - SKELETAL-MUSCLE

KW - MYOSIN

KW - MELANOGASTER

KW - PROTEINS

KW - MUTAGENESIS

KW - SURFACE

KW - COMPLEX

KW - REMOVAL

KW - INSECTS

M3 - Article

SN - 0022-2836

VL - 295

SP - 1201

EP - 1210

JO - Journal of Molecular Biology

JF - Journal of Molecular Biology

IS - 5

ER -