5fa8
SAM complex with aKMT from the hyperthermophilic archaeon Sulfolobus islandicuSAM complex with aKMT from the hyperthermophilic archaeon Sulfolobus islandicu
Structural highlights
FunctionPublication Abstract from PubMedProtein methylation is believed to occur extensively in creanarchaea. Recently, aKMT, a highly conserved crenarchaeal protein lysine methyltransferase, was identified and shown to exhibit broad substrate specificity in vitro. Here, we have constructed an aKMT deletion mutant (DeltaaKMT) of the hyperthermophilic crenarchaeon Sulfolobus islandicus. The mutant was viable but showed a moderately slower growth rate than the wild type strain under non-optimal growth conditions. Consistent with the moderate effect of the lack of aKMT on the growth of the cell, expression of a small number of genes, which encode putative functions in substrate transportation, energy metabolism, transcriptional regulation, stress response proteins, etc, was differentially regulated by more than 2 fold in the mutant strain, as compared to that in the wild type strain. Analysis of the methylation of total cellular protein by mass spectrometry revealed that methylated proteins accounted for ~2/3 (1,158/1,750) and ~1/3 (591/1,766) of the identified proteins in the wild type and the mutant strains, respectively, indicating that there is extensive protein methylation in S. islandicus and that aKMT is a major protein methyltransferase in this organism. No significant sequence or secondary structural preference was detected at the sites of methylation by aKMT. The crystal structure of aKMT in complex with S-adenosyl-L-methionine (SAM) or S-adenosyl homocysteine (SAH) reveals that the protein consists of four alpha helices and seven beta sheets, lacking a substrate recognition domain found in PrmA, a bacterial homolog of aKMT, in agreement with the broad substrate specificity of aKMT. Our results suggest that aKMT may serve a role in maintaining the methylation status of cellular proteins required for the efficient growth of the organism under certain non-optimal conditions. aKMT catalyzes extensive protein lysine methylation in the hyperthermophilic archaeon Sulfolobus islandicus but is dispensable for the growth of the organism.,Chu Y, Zhu Y, Chen Y, Li W, Zhang Z, Liu D, Wang T, Ma J, Deng H, Liu ZJ, Ouyang S, Huang L Mol Cell Proteomics. 2016 Jun 21. pii: mcp.M115.057778. PMID:27329856[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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