title: Varied metal-binding properties of lipoprotein PsaA in Streptococcus pneumoniae.
abstract: Streptococcus pneumoniae is a Gram-positive pathogen responsible for pneumonia, otitis media, and meningitis. Manganese and zinc ions are essential for this bacterium, playing regulatory, structural, or catalytic roles as the critical cofactors in the bacterial proteins and metabolic enzymes. Lipoprotein PsaA has been found to mediate Mn(2+) and Zn(2+) transportation in Streptococcus pneumoniae. In the present work, we conducted a systemic study on the contributions from key amino acids in the metal-binding site of PsaA using various spectroscopic and biochemical methods. Our experimental data indicate that four metal-binding residues contribute unequally to the Mn(2+) and Zn(2+) binding, and His139 is most important for both the structural stability and metal binding of the protein. PsaA-Mn(2+) has a lower thermal stability than PsaA-Zn(2+), possibly due to the different coordination preferences of the metals. Kinetics analysis revealed that PsaA-Mn(2+) binding is a fast first-order reaction, whereas PsaA-Zn(2+) binding is a slow second-order reaction, implying that PsaA kinetically prefers binding Mn(2+) to Zn(2+). The present results provide complementary information for understanding the mechanisms of metal transport and bacterial virulence via lipoproteins in Streptococcus pneumoniae.
authors.affiliation: Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, College of Life Science and Technology, Jinan University, Guangzhou, 510632, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Li
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Yang
authors.forename: Zhong
authors.initials: Z
authors.lastname: Guo
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Kun
authors.initials: K
authors.lastname: Cao
authors.forename: Junlong
authors.initials: J
authors.lastname: Han
authors.forename: Gong
authors.initials: G
authors.lastname: Zhang
authors.forename: Langxia
authors.initials: L
authors.lastname: Liu
authors.forename: Xuesong
authors.initials: X
authors.lastname: Sun
authors.forename: Qing-Yu
authors.initials: QY
authors.lastname: He
mesh_terms: D018829:Adhesins, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D007700:Kinetics; D008074:Lipoproteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D013296:Streptococcus pneumoniae / Q000737:chemistry* / Q000378:metabolism; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
chemical_list: D018829:Adhesins, Bacterial; D008074:Lipoproteins; C085000:PsaA protein, Streptococcus; D008345:Manganese; D015032:Zinc