Structures of two Arabidopsis thaliana major latex proteins represent novel helix-grip folds.

The major latex proteins (MLP) are a protein family first identified in the latex of opium poppy. They are found only in plants and have 24 identified members in alone as well as in other plants such as peach, strawberry, melon, cucumber, and soybean. While the function of the MLPs is unknown, they have been associated with fruit and flower development and in pathogen defense responses.

Structural basis of CXCR4 sulfotyrosine recognition by the chemokine SDF-1/CXCL12.

Stem cell homing and breast cancer metastasis are orchestrated by the chemokine stromal cell-derived factor 1 (SDF-1) and its receptor CXCR4. Here, we report the nuclear magnetic resonance structure of a constitutively dimeric SDF-1 in complex with a CXCR4 fragment that contains three sulfotyrosine residues important for a high-affinity ligand-receptor interaction. CXCR4 bridged the SDF-1 dimer interface so that sulfotyrosines sTyr7 and sTyr12 of CXCR4 occupied positively charged clefts on opposing chemokine subunits.

Solution structure of At3g28950 from Arabidopsis thaliana.

We determined the solution structure of At3g28950 from A. thaliana, a homolog of At5g39720, whose structure we solved earlier. The secondary structure of the 165-aa protein consists of a 5-strand antiparallel beta-barrel domain flanked by two alpha-helices and a 2-strand beta-sheet; an additional free C-terminal alpha-helix extends into solution.

Solution structure of a membrane-anchored ubiquitin-fold (MUB) protein from Homo sapiens.

The protein Bc059385, whose solution structure is reported here, is the human representative of a recently identified family of membrane-anchored ubiquitin-fold (MUB) proteins. Analysis of their similarity to ubiquitin indicates that homologous amino acid residues in MUBs form a hydrophobic surface very similar to the recognition patch surrounding Ile-44 in ubiquitin. This suggests that MUBs may interact with proteins containing an alpha-helical motif similar to those of some ubiquitin binding domains.