How in typescript declare an interface key as specific type?

I have the interface:

export type TCategoryAnalyzes = {
  categoryId: string,
  analyzes: IAnalyzesStorageData[],
  region: string,
};

The goal is to make it something like:

export type TCategoryAnalyzes = {
  region: { // string
    categoryId: string,
    analyzes: IAnalyzesStorageData[],
  }
};

Where the region key must be of a string type

export type TCategoryAnalyzes = {
  [region: string]: {
    categoryId: string;
    analyzes: IAnalyzesStorageData[];
  };
};

this his how you can achieve it.