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Methylhistidine Analysis Essay

Abstract

MRP14 (macrophage migration-inhibitory factor-related protein of molecular mass 14 kDa) is an S100 calcium binding protein constitutively expressed in human neutrophils which may be associated with cellular activation/inflammation. Murine MRP14 expression was up-regulated following concanavalin A activation of spleen cells, and the protein was isolated from conditioned medium in high yield (approx. 500 ng/ml). MRP14 had a mass of 12972±2 Da by electrospray ionization MS, whereas the theoretical mass derived from the cDNA sequence, after removal of the initiator Met, was 12918 Da, suggesting that the protein was post-translationally modified. We identified four post-translational modifications of MRP14: removal of the N-terminal Met, N-terminal acetylation, disulphide bond formation between Cys79 and Cys90, and 1-methylation of His106; the calculated mass was then 12971.8 Da. Methylation of His106 was further characterized after incubation of spleen cells with L-[methyl-3H]Met during concanavalin A stimulation. Sequential analysis of a peptide (obtained by digestion with Lys C) containing methylated His indicated that > 80% of the label in the cycle corresponded to His106, suggesting that the methyl residue was transferred from S-adenosyl-L-methionine. Comparison of the C18 reverse-phase HPLC retention times of phenylthiocarbamoyl derivatives of a hydrolysed digest peptide of MRP14 with those of standards confirmed methyl substitution on the 1-position of the imidazole ring. MRP14 bound more 65Zn2+ than the same amounts of the 10 kDa chemotactic protein (CP10) or S100β. Ca2+ decreased Zn2+ binding in S100β but it did not influence binding to MRP14, suggesting that the Zn2+ binding site was distinct from and independent of the two Ca2+ binding domains.

  • The Biochemical Society, London © 1996

Don't panic when your instructor tells you that you need to write an analysis!  All he or she wants is for you to take something apart to see HOW it works.

To write an analysis, you need to think about how each part of something contributes to the success of the whole.

Caution!  Make sure that you're NOT just summarizing the original article, story, novel, poem, etc.  Go beyond simply telling us WHAT you are talking about: describe HOW and WHY its elements function.

Specific Information for Analyzing Literature

Summarizing = WHAT
Analyzing = HOW & WHY

When you think about analysis, try thinking about how you might analyze a car.

  • Ask yourself: What do we want the car to do or accomplish?
    • Answer: (minivan) “provide transportation for my family”
      • Analysis: how does each part of the van achieve this goal?
        • Example: gasoline powers the engine
    • Answer: (sports car) “speed, agility, and style”
      • Analysis: how does each part of the sports car achieve this goal?
        • Example:  light-weight construction enables speed

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