
@article {86518,
	title = {Structure and Function of -Acetylmannosamine Kinases from Pathogenic Bacteria.},
	journal = {ACS Omega},
	volume = {5},
	year = {2020},
	month = {2020 Dec 08},
	pages = {30923-30936},
	abstract = {<p>Several pathogenic bacteria import and catabolize sialic acids as a source of carbon and nitrogen. Within the sialic acid catabolic pathway, the enzyme -acetylmannosamine kinase (NanK) catalyzes the phosphorylation of -acetylmannosamine to -acetylmannosamine-6-phosphate. This kinase belongs to the ROK superfamily of enzymes, which generally contain a conserved zinc-finger (ZnF) motif that is important for their structure and function. Previous structural studies have shown that the ZnF motif is absent in NanK of (-NanK), a Gram-negative bacterium that causes the gum disease gingivitis. However, the effect in loss of the ZnF motif on the kinase activity is unknown. Using kinetic and thermodynamic studies, we have studied the functional properties of -NanK to its substrates ManNAc and ATP, compared its activity with other ZnF motif-containing NanK enzymes from closely related Gram-negative pathogenic bacteria (-NanK), (-NanK), and (-NanK). Our studies show a 10-fold decrease in substrate binding affinity between NanK (apparent ≈ 700 μM) and ZnF motif-containing NanKs (apparent ≈ 60 μM). To understand the structural features that combat the loss of the ZnF motif in -NanK, we solved the crystal structures of functionally homologous ZnF motif-containing NanKs from and . Here, we report -NanK:unliganded, -NanK:AMPPNP, -NanK:ManNAc, -NanK:ManNAc, and -NanK:ManNAc-6P:ADP crystal structures. Structural comparisons of -NanK with -NanK, -NanK, and hMNK (human -acetylmannosamine kinase domain of UDP--acetylglucosamine-2-epimerase/-acetylmannosamine kinase, GNE) show that even though there is less sequence identity, they have high degree of structural similarity. Furthermore, our structural analyses highlight that the ZnF motif of -NanK is substituted by a set of hydrophobic residues, which forms a hydrophobic cluster that helps the proper orientation of ManNac in the active site. In summary, ZnF-containing and ZnF-lacking NanK enzymes from different Gram-negative pathogenic bacteria are functionally very similar but differ in their metal requirement. Our structural studies unveil the structural modifications in -NanK that compensate the loss of the ZnF motif in comparison to other NanK enzymes.</p>
},
	issn = {2470-1343},
	doi = {10.1021/acsomega.0c03699},
	author = {Gangi Setty, Thanuja and Sarkar, Arunabha and Coombes, David and Dobson, Renwick C J and Subramanian, Ramaswamy}
}
@article {65299,
	title = {Serotonin is essential for eye regeneration in planaria Schmidtea mediterranea.},
	journal = {FEBS Lett},
	year = {2019},
	month = {2019 Sep 17},
	abstract = {<p>Planaria is an ideal system to study factors involved in regeneration and tissue homeostasis. Little is known about the role of metabolites and small molecules in stem cell maintenance and lineage specification in planarians. Using liquid chromatography and mass spectrometry (LC-MS)-based quantitative metabolomics, we determined the relative levels of metabolites in stem cells, progenitors, and differentiated cells of the planarian Schmidtea mediterranea. Tryptophan and its metabolic product serotonin are significantly enriched in stem cells and progenitor population. Serotonin biosynthesis in these cells is brought about by a non-canonical enzyme, phenylalanine hydroxylase (PAH). Knockdown of Smed-pah leads to complete disappearance of eyes in regenerating planaria, while exogenous supply of serotonin and its precursor rescue the eyeless phenotype. Our results demonstrate a key role for serotonin in eye regeneration.</p>
},
	issn = {1873-3468},
	doi = {10.1002/1873-3468.13607},
	author = {Sarkar, Arunabha and Mukundan, Namita and Sowndarya, Sai and Dubey, Vinay Kumar and Babu, Rosana and Lakshmanan, Vairavan and Rangiah, Kannan and Panicker, Mitradas M and Palakodeti, Dasaradhi and Subramanian, Sabarinath Peruvemba and Ramaswamy, Subramanian}
}
