The secondary structure for two murine recombinant proteins, interleukins 1 alpha and 1 beta (rmIL-1 alpha and -1 beta), has been analyzed by Fourier transform infrared (IR) spectroscopy and then compared to results obtained by X-ray diffraction, circular dichroism (CD), and nuclear magnetic resonance (NMR) spectroscopy. The IR results obtained here for rmIL-1 alpha and -1 beta suggested that their secondary structures consisted predominantly of beta-sheets or strands. However, the analysis also revealed a significant absorption band near 1656 cm-1, which is typically assigned to alpha-helical or random structures. When these same murine polypeptides were analyzed by CD, no evidence of alpha-helical structures was observed. Further, published X-ray diffraction and NMR studies characterizing the human forms of IL-1 alpha and -1 beta indicate the absence of alpha-helices and that the human proteins are composed mainly of beta-strands (i.e., greater than 55%), with approximately 24% of the amino acids involved in large loops connecting the strands. The murine IL-1 proteins, when compared to their respective human counterparts, each show greater than 80% sequence homology. Given this fact, the CD analyses, and the result that this IR band amounted to 21% of the overall integrated area, the absorption peak at 1656 cm-1 was attributed to the presence of large loops rather than to alpha-helical or random structures. Such a structural assignment appears reasonable and is totally consistent with the established existence of large loops in the human forms as well as in other proteins found to fold similarly (viz., human bFGF).(ABSTRACT TRUNCATED AT 250 WORDS)
The plasma form of the human enzyme platelet activating factor acetylhydrolase (PAF-AH) has been crystallized, and X-ray diffraction data were collected at a synchrotron source to a resolution of 1.47 Å. The crystals belong to space group C2, with unit cell parameters of a = 116.18, b = 83.06, c = 96.71 Å, and β = 115.09° and two molecules in the asymmetric unit. PAF-AH functions as a general anti-inflammatory scavenger by reducing the levels of the signaling molecule PAF. Additionally, the LDL bound enzyme has been linked to atherosclerosis due to its hydrolytic activities of pro-inflammatory agents, such as sn-2 oxidatively fragmented phospholipids.
A biologically active preparation of murine recombinant interleukin‐1β (mIL‐1β) fromEscherichia coli cell lysates contained two forms of mIL‐1β with pI 8.7 and pI 8.1, respectively. Treatment with 0.1 M Tris, pH 8.5, at 37°C for 35 h converted the pI 8.7 form to the pI 8.1 form by the selective deamidation of an asparagine residue (Asn149) in the mIL‐1β molecule. Deamidated mIL‐1β had 3‐ to 5‐fold lower co‐mitogenic activity and receptor affinity than the unmodified form.
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