Molecular basis for N-terminal acetylation by the heterodimeric NatA complex

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• N-terminal acetylation is a widespread post-translational modification in eukaryotes, regulating diverse biological processes.
• The NatA complex, a heterodimeric N-terminal acetyltransferase (NAT), is responsible for acetylating the majority of N-terminally acetylated proteins and exhibits broad substrate specificity.

Purpose of the Study:

• To elucidate the structural basis of NatA complex function using X-ray crystallography.
• To understand how the auxiliary subunit (Naa15p) influences the catalytic subunit (Naa10p) activity and substrate specificity.

Main Methods:

• X-ray crystallography was employed to determine the structure of the holo-NatA complex from Schizosaccharomyces pombe.
• Structures were obtained for the complex alone, in the presence of a peptide-CoA-conjugate inhibitor, and for the uncomplexed Naa10p catalytic subunit.

Main Results:

• The 100-kDa holo-NatA complex structure revealed a ring-like topology of the Naa15p auxiliary subunit, which encircles the Naa10p catalytic subunit.
• This interaction significantly alters the active site of Naa10p, enabling substrate-specific acetylation.
• The structure of the uncomplexed Naa10p catalytic subunit was also determined.

Conclusions:

• The structural insights into the NatA complex provide a mechanistic understanding of how auxiliary subunits modulate NAT activity.
• This work has implications for understanding other NAT complexes and the broader family of protein acetyltransferases.