Abstract
N-terminal acetylation (NTA) is a highly abundant protein modification catalyzed by N-terminal acetyltransferases (NATs) in eukaryotes. However, the plant NATs and their biological functions have been poorly explored. Here we reveal that loss of function of CKRC3 and NBC-1, the auxiliary subunit (Naa25) and catalytic subunit (Naa20) of Arabidopsis NatB, respectively, led to defects in skotomorphogenesis and triple responses of ethylene. Proteome profiling and WB test revealed that the 1-amincyclopropane-1-carboxylate oxidase (ACO, catalyzing the last step of ethylene biosynthesis pathway) activity was significantly down-regulated in natb mutants, leading to reduced endogenous ethylene content. The defective phenotypes could be fully rescued by application of exogenous ethylene, but less by its precursor ACC. The present results reveal a previously unknown regulation mechanism at the co-translational protein level for ethylene homeostasis, in which the NatB-mediated NTA of ACOs render them an intracellular stability to maintain ethylene homeostasis for normal growth and responses.
Highlights
N-terminal acetylation (NTA) is a form of a highly abundant co- or post-translational protein modification in eukaryotes, in which the α-amino group of a protein’s Nterminal amino acid is acetylated under the catalysis of N-terminal acetyltransferases (NATs) [1, 2]
NatB is required for normal growth of Arabidopsis Previously an Arabidopsis mutant named ckrc3 caused by loss of function mutation of the gene encoding the auxiliary subunit (Naa25/TCU2) of a putative Nα-terminal acetyltransferase B (NatB) was isolated as an auxin-deficient mutant in our lab
NatB is one of the eight Nats (NatA - NatH) found so far in eukaryotes, containing a catalytic (Naa20) and an auxiliary subunit (Naa25) to perform its full intracellular functions by cotranslationally catalyzing the NTA of proteins beginning with MD/E/N/Q, as confirmed in our former experiments and others
Summary
N-terminal acetylation (NTA) is a form of a highly abundant co- or post-translational protein modification in eukaryotes, in which the α-amino group of a protein’s Nterminal amino acid is acetylated under the catalysis of N-terminal acetyltransferases (NATs) [1, 2]. NATs are classified as NatA-NatH based on substrate specificity and subunit compositions, which consist of at least one catalytic subunit and auxiliary subunit [3, 4]. The auxiliary subunits can function as a ribosome anchor, providing substrate specificity, and/or interaction with nascent polypeptides [5]. For decades it was believed that ACS is the rate-limiting enzyme of this pathway, promoting studies to investigate the regulation of ACS at different levels. Emerging evidences in recent years reveal that ACO can be rate-limiting in ethylene production under certain circumstances [19], implying that the ACOs may be subjected to a stringent regulation, but its molecular mechanisms is so far
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
