title: Oligomerization, conformational stability and thermal unfolding of Harpin, HrpZPss and its hypersensitive response-inducing c-terminal fragment, C-214-HrpZPss.
abstract: HrpZ-a harpin from Pseudomonas syringae-is a highly thermostable protein that exhibits multifunctional abilities e.g., it elicits hypersensitive response (HR), enhances plant growth, acts as a virulence factor, and forms pores in plant plasma membranes as well as artificial membranes. However, the molecular mechanism of its biological activity and high thermal stability remained poorly understood. HR inducing abilities of non-overlapping short deletion mutants of harpins put further constraints on the ability to establish structure-activity relationships. We characterized HrpZPss from Pseudomonas syringae pv. syringae and its HR inducing C-terminal fragment with 214 amino acids (C-214-HrpZPss) using calorimetric, spectroscopic and microscopic approaches. Both C-214-HrpZPss and HrpZPss were found to form oligomers. We propose that leucine-zipper-like motifs may take part in the formation of oligomeric aggregates, and oligomerization could be related to HR elicitation. CD, DSC and fluorescence studies showed that the thermal unfolding of these proteins is complex and involves multiple steps. The comparable conformational stability at 25°C (∼10.0 kcal/mol) of HrpZPss and C-214-HrpZPss further suggest that their structures are flexible, and the flexibility allows them to adopt proper conformation for multifunctional abilities.
authors.affiliation: School of Chemistry, University of Hyderabad, Hyderabad, India.
authors.forename: Pradip K
authors.initials: PK
authors.lastname: Tarafdar
authors.affiliation: Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India.
authors.forename: Lakshmi Vasudev
authors.initials: LV
authors.lastname: Vedantam
authors.affiliation: School of Chemistry, University of Hyderabad, Hyderabad, India.
authors.forename: Rajeshwer S
authors.initials: RS
authors.lastname: Sankhala
authors.affiliation: Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India.
authors.forename: Pallinti
authors.initials: P
authors.lastname: Purushotham
authors.affiliation: Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India.
authors.forename: Appa Rao
authors.initials: AR
authors.lastname: Podile
authors.affiliation: School of Chemistry, University of Hyderabad, Hyderabad, India.
authors.forename: Musti J
authors.initials: MJ
authors.lastname: Swamy
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D016350:Leucine Zippers; D008958:Models, Molecular; D055503:Protein Multimerization; D055550:Protein Stability; D058767:Protein Unfolding; D044224:Pseudomonas syringae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; C087295:HrpZ protein, Pseudomonas syringae