Plant and algal prolyl 4-hydroxylases (P4Hs) are key enzymes in the synthesis of cell wall components. These monomeric enzymes belong to the 2-oxoglutarate dependent superfamily of enzymes characterized by a conserved jelly-roll framework. This algal P4H has high sequence similarity to the catalytic domain of the vertebrate, tetrameric collagen P4Hs, whereas there are distinct sequence differences with the oxygen-sensing hypoxia-inducible factor P4H subfamily of enzymes. We present here a 1.98-Å crystal structure of the algal Chlamydomonas reinhardtii P4H-1 complexed with Zn 2؉ and a proline-rich (SerPro) 5 substrate. This ternary complex captures the competent mode of binding of the peptide substrate, being bound in a lefthanded (poly)L-proline type II conformation in a tunnel shaped by two loops. These two loops are mostly disordered in the absence of the substrate. The importance of these loops for the function is confirmed by extensive mutagenesis, followed up by enzyme kinetic characterizations. These loops cover the central Ser-Pro-Ser tripeptide of the substrate such that the hydroxylation occurs in a highly buried space. This novel mode of binding does not depend on stacking interactions of the proline side chains with aromatic residues. Major conformational changes of the two peptide binding loops are predicted to be a key feature of the catalytic cycle. These conformational changes are probably triggered by the conformational switch of Tyr 140 , as induced by the hydroxylation of the proline residue. The importance of these findings for understanding the specific binding and hydroxylation of (X-Pro-Gly) n sequences by collagen P4Hs is also discussed.

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BackgroundDeliberate self-harm (DSH) is an act with a non-fatal outcome in which an individual initiates a behavior, such as self-cutting or burning, with the intention of inflicting harm on his or her self. Interpersonal difficulties have been shown to be a risk factor for DSH, but the association between subjective experience of loneliness and DSH have rarely been examined.ObjectiveTo examine the frequency of DSH or its ideation and loneliness among 16-year-olds to determine if associations exist between DSH and loneliness, loneliness-related factors, self-rated health and satisfaction with life.DesignThe study population (n=7,014) was taken from Northern Finland Birth Cohort 1986 (N=9,432). Cross-tabulations were used to describe the frequency of DSH by factors selected by gender. Logistic regression analysis was used to describe the association between DSH and loneliness and other selected factors.ResultsNearly 8.7% (n=608) of adolescents reported DSH often/sometimes during the preceding 6 months, with girls (n=488, 13.4%) reporting DSH almost 4 times than that of boys (n=120, 3.6%). Nearly 3.2% of the adolescents (girls: n=149, 4.1%; boys: n=72, 2.2%) expressed that the statement I feel lonely was very/often true, and 26.4% (girls: n=1,265, 34.8%; boys: n=585, 17.4%) expressed that the statement was somewhat/sometimes true. Logistic regression showed that those who reported to be very/often lonely (girls: odds ratio (OR) 4.1; boys: OR 3.2), somewhat/sometimes lonely (girls: OR 2.4; boys: OR 2.4) were dissatisfied with life (girls: OR 3.3; boys: OR 3.3), felt unliked (girls: OR 2.2; boys: OR 6.0) and had moderate self-rated health (girls: OR 2.0; boys: OR 1.7), were more likely to report DSH than those without these feelings.ConclusionThe results show that loneliness is associated with DSH, and that loneliness should be considered as a risk for individual health and well-being.

a faculty of education, Women's and Gender studies, university of oulu, oulu, finland; b center for life course health research, university of oulu, oulu, finland; c centre for arctic Medicine, thule Institute, university of oulu, oulu, finland