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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Healthy Processed Foods Research » Research » Publications at this Location » Publication #355260

Research Project: Defining, Measuring, and Mitigating Attributes that Adversely Impact the Quality and Marketability of Foods

Location: Healthy Processed Foods Research

Title: Crystal structure of the Streptococcus agalactiae CAMP Factor, and insights into its membrane-permeabilizing activity

item JIN, TENGCHUAN - University Of Science And Technology Of China
item BREFO-MENSAH, ERIC - University Of Waterloo
item FAN, WEIRONG - Shanghai Jiaotong University
item ZENG, WEIHONG - Tianjin University Of Science And Technology
item LI, YAJUAN - University Of Science And Technology Of China
item Zhang, Yuzhu
item PALMER, MICHAEL - University Of Waterloo

Submitted to: Journal of Biological Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2018
Publication Date: 6/8/2018
Citation: Jin, T., Brefo-Mensah, E., Fan, W., Zeng, W., Li, Y., Zhang, Y., Palmer, M. 2018. Crystal structure of the Streptococcus agalactiae CAMP Factor, and insights into its membrane-permeabilizing activity. Journal of Biological Chemistry. 293:11867-11877.

Interpretive Summary: Streptococcus agalactiae (group B streptococcus; GBS) can cause serious illness, particularly among infant, elderly, and in immune-compromised patients. Asymptomatic GBS colonization is common. The bacterium resides in the vagina or rectum of about 25% of all healthy adult women in the US. GBS is an important cause of contagious mastitis in cattle, and it is also a fish pathogen. Thus, it represents a zoonotic hazard that may compromise food safety. The CAMP factor is expressed in virtually all S. agalactiae strains. In the membranes of sphingomyelinase-pretreated sheep red blood cells, CAMP attaches to the cell membrane and forms circular pores. However, the mechanism of CAMP’s activity at the molecular level and the structural details of this toxin are unknown. This study reports the three-dimensional structure of CAMP factor for the first time and describes biochemical experiments that assign functional roles to the CAMP domains. Knowledge of the structure of the pore-forming protein toxin will facilitate more detailed biophysical studies to better understand its interaction with host cell membranes. Such studies may result critical information for the prevention of future food safety events related GBS pathogens.

Technical Abstract: CAMP factor is a pore-forming toxin from Group B streptococci (GBS), which is commonly used to identify this pathogen in clinical microbiology. Closely related proteins occur in other Gram-positive pathogens. Here, we report the first structure of this protein, which defines a novel structural fold composed of 5+3 helix bundles. Truncation and site-directed mutagenesis analysis indicate that the N-terminal 5 helix bundle is responsible for membrane permeabilization, while its C-terminal 3 helix bundle is likely responsible for receptor binding.