Hydroxyproline-rich glycoproteins (HRGPs) are the major proteinaceous components of higher plant walls and the predominant components of the cell wall of the green alga Chlamydomonas reinhardtii. The GP1 protein, an HRGP of the C. reinhardtii wall, is shown to adopt a polyproline II helical configuration and to carry a complex array of arabinogalactoside residues, many branched, which are necessary to stabilize the helical conformation. The deduced GP1 amino acid sequence displays two Ser-Pro-rich domains, one with a repeating (SP)(x)() motif and the other with a repeating (PPSPX)(x)() motif. A second cloned gene a2 also carries the PPSPX repeat, defining a novel gene family in this lineage. The SP-repeat domains of GP1 form a 100-nm shaft with a flexible kink 28 nm from the head. The gp1 gene encodes a PPPPPRPPFPANTPM sequence at the calculated kink position, generating the proposal that this insert interrupts the PPII helix, with the resultant kink exposing amino acids necessary for GP1 to bind to partner molecules. It is proposed that similar kinks in the higher plant HRGPs called extensins may play a comparable role in wall assembly.

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Mass determination by mass spectrometric methods (electrospray ionization mass spectrometry (ESI-MS), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS)) of sodiumdodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE)-separated proteins is a well known procedure and reliable protocols are available. In our efforts to use the established methods to determine the molecular mass of the disulfide bridged, heterodimeric glycoprotein GP3 and to determine the carbohydrate content of each protein subunit we developed an in-gel chemical deglycosylation method. For this purpose we established experimental conditions that allow maximum extraction of the high molecular mass protein subunits and developed a routine method to apply the HF-pyridine deglycosylation protocol to proteins isolated from polyacrylamide gel pieces. The novel protocol and extraction procedure described can be used to analyze O-glycosylated proteins up to 150 kDa after SDS-PAGE separation.

Pseudomonas fluorescens, Pseudomonas putida, Pyoverdine, Siderophore, Bacterial Classification From Pseudom onas fluorescens 9AW and from Pseudomonas putida 9BW identical pyo-verdine-type siderophores were isolated and their structures were elucidated by spectroscopic methods and degradation studies. These novel compounds are of interest as they contain L-threo-β-hydroxy histidine in their peptide chains, an amino acid sofar encountered in nature only rarely. The co-occurence of the same pyoverdine in different Pseudom onas species and its significance for the classification is discussed.