title: Interaction of fibronectin type II proteins with membranes: the stallion seminal plasma protein SP-1/2.
abstract: Seminal plasma of mammalians contains, among others, proteins that are characterized by the fibronectin (Fn) type II module. Our knowledge about the structure and the physiological function of seminal Fn type II proteins mainly originates from studies on PDC-109, the bovine representative of this protein family. The present work focuses on the equine protein SP-1/2 (also named HSP-1/2) with particular emphasis on its interaction with lipid membranes by employing the intrinsic protein fluorescence and a number of spin-labeled and fluorescent lipid analogues. The results indicate that the interaction of SP-1/2 with (lipid) membranes is similar to that of PDC-109 which can be explained by homologous amino acid sequences of both proteins. Like PDC-109, SP-1/2 has a specificity for phospholipids with the phosphocholine headgroup. Upon binding to lipid vesicles, the protein intercalates into the hydrophobic membrane core, resulting in a rigidification of the lipid phase and, at higher concentration, in a perturbation of membrane structure. However, compared with PDC-109, the impact of SP-1/2 on membranes is less intense in that the degree of protein-mediated immobilization of lipids was lower. Furthermore, different to PDC-109, SP-1/2 was not able to extract lipids from human red blood cells. The data are discussed with regard to similarities and species-specific differences of the function of seminal Fn type II proteins in the genesis of sperm cells.
authors.affiliation: Institut für Biologie, Mathematisch-Naturwissenschaftliche Fakultät I, Humboldt-Universität zu Berlin, Invalidenstrasse 43, D-10115 Berlin, Germany.
authors.forename: Alexa
authors.initials: A
authors.lastname: Greube
authors.forename: Karin
authors.initials: K
authors.lastname: Müller
authors.forename: Edda
authors.initials: E
authors.lastname: Töpfer-Petersen
authors.forename: Andreas
authors.initials: A
authors.lastname: Herrmann
authors.forename: Peter
authors.initials: P
authors.lastname: Müller
mesh_terms: D020816:Amino Acid Motifs; D000731:Androstanes / Q000737:chemistry; D000818:Animals; D002417:Cattle; D002776:Cholestanes / Q000737:chemistry; D002784:Cholesterol / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D004910:Erythrocyte Membrane / Q000737:chemistry; D005353:Fibronectins / Q000737:chemistry* / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D006736:Horses; D006801:Humans; D008081:Liposomes; D008297:Male; D008563:Membrane Lipids / Q000737:chemistry* / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry; D029589:Seminal Plasma Proteins / Q000737:chemistry* / Q000378:metabolism; D029607:Seminal Vesicle Secretory Proteins / Q000737:chemistry; D013113:Spin Labels
chemical_list: D000731:Androstanes; D002776:Cholestanes; D005353:Fibronectins; D008081:Liposomes; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D029589:Seminal Plasma Proteins; D029607:Seminal Vesicle Secretory Proteins; D013113:Spin Labels; C424303:seminal vesicle secretory protein 109, Bos taurus; D002784:Cholesterol; C033936:androstane