Part:BBa_K5246011
CB2/CB2A HfsK Acetyltransferase
Introduction
Usage and Biology
The HfsK gene from Caulobacter crescentus encodes an acetyltransferase protein of 359aa. HfsK is a c-di-GMP effector involved in holdfast biogenesis. Cells lacking HfsK form highly malleable holdfast structures with reduced adhesive strength that cannot support surface colonization. HfsK is a soluble protein but associates with the cell membrane during most of the cell cycle but is transfered to cytosol in the process of holdfast synthesis. HfsK deacetylates N-acetyl-glucosamine from the holdfast, which results in better adhesive properties.
Sequence and Features
- 10INCOMPATIBLE WITH RFC[10]Illegal PstI site found at 64
- 12INCOMPATIBLE WITH RFC[12]Illegal PstI site found at 64
- 21INCOMPATIBLE WITH RFC[21]Illegal XhoI site found at 793
- 23INCOMPATIBLE WITH RFC[23]Illegal PstI site found at 64
- 25INCOMPATIBLE WITH RFC[25]Illegal PstI site found at 64
- 1000COMPATIBLE WITH RFC[1000]
Experimental characterization
Bioinformatic analysis
Using CDD analysis, it was identified that HfsK is similar to the GNAT N-acetyltransferase family. It has domains that suggest HfsK is part of the Bcls superfamily. Usually, acetyltransferases of this superfamily are involved in cellulose biosynthesis. Protein BLAST did not give conclusive results, which could be the result of a unique HfsK protein amino acid sequence and structure.
Protein topology predictions by DeepTMHMM showed that HfsK is most likely a globular protein located on the cytoplasmic side of the membrane.
High confidence scores of AlphaFold3 structures suggest that HfsK is likely a globular protein. A pTM score above 0.5 suggests that the predicted overall structure may closely resemble the true protein fold, while ipTM indicates the accuracy of the subunit positioning within the complex. Values higher than 0.8 represent confident high-quality predictions (Fig.1).
To summarise, HfsK is most likely a globular N-acetyltransferase. Earlier evidence, combined with our findings, suggests that it plays a role in the deacetylation of N-acetylglucosamine within the holdfast synthesis pathway. [1][2][3]
References
1. Chepkwony, N.K. and Brun, Y.V. (2021) ‘A polysaccharide deacetylase enhances bacterial adhesion in high-ionic-strength environments’, iScience, 24(9), p. 103071. doi:10.1016/j.isci.2021.103071.
2. Sprecher, K.S. et al. (2017) ‘Cohesive properties of the Caulobacter crescentus holdfast adhesin are regulated by a novel C-di-GMP effector protein’, mBio, 8(2). doi:10.1128/mbio.00294-17.
3. Hershey, D.M., Fiebig, A. and Crosson, S. (2019) ‘A genome-wide analysis of adhesion in Caulobacter crescentus identifies new regulatory and biosynthetic components for holdfast assembly’, mBio, 10(1). doi:10.1128/mbio.02273-18.
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